I'm gonna assume a marching order of Sekkar - Kaylyn - Sarith - Zeno - Shuushar - Kastix - Rhayna/Stool - Jimjar - Derendil - Joetaro.
Let me know if that doesn't fit anyone's expectations.

The blue are the unarmed, the red are the staff-wielders. All kuo-toa are standing on a ledge five feet higher than the characters.

Five fit is not a distance even for a bad jumper - Sekkar can manage. If there is a space on the ledge - he would jump there and attack first n10, then n11. If not, he can still jump up and attack that way.

(Zeno would probably normally be up front scouting with Sekkar, but no need to change the order for this fight)

Just waiting for Kaylyn's Initiative and Action

Sarith: 18, Jimjar: 14, Derendil: 3

Initiative 16

 Kaylyn sends a blast of Eldritch Energy at the one in slot 2 that has a staff

Attack: 16 + 3 (Bless) Damage: 10

ROUND 1

Being toward the front (or naturally observant), Rhayna, Sarith and Sekkar are the first to act, with the cleric praying for divine help on her friends, and the warriors lashing out at the attackers with their swords. Sekkar's blade bites into fishy flesh but Sarith's swing hits the kuo-toa's shield and is then somehow ripped from his grasp! While Zeno appeals for calm, Kastix and Kaylyn fire their spells at their attackers, and burn holes in the scaly skin of the fish-folk, which unexpectedly makes a few mouths water with hunger. As those at the back of the column join the dray, Jimjar throws a dagger on each side, and Derendil lashes out with his claws, while Joetaro's spell makes everyone at the back of the line drowsy, sending two of the kuo-toa to sleep as their spears clatter to the ground.

One kuo-toa hears Zeno's plea, by rather than reply to Zeno is calls out to its comrades: Ez dugu heretikoa hiltzen. Aita sakonaren gurtzera aurkeztu behar da. Seeing they are not going to relent, Zeno manages to squeeze off his crossbow as the kuo-toa on the left ledge cast their nets down on their prey. They are obviously experts at net-casting, and soon almost everyone is tangled in wet rope as the kuo-toa on the right ledge stab down with their spears. Only Derendil and Kaylyn manage to avoid the nets, although the warlock is grabbed around the shoulder by one of the pincer-shaped staves, which have small spikes that make resistance particularly painful. The two unarmed kuo-toa lash out with their large webbed feet at Sekkar and Joetaro, and each successful strike is accompanied by a painful shock of electricity, as if stung by an eel. Again the kuo-toa voice is heard above the din: Errendizio!

Everyone (except Derendil) is restrained by nets, plus Kaylyn is grappled by the pincer staff. I've never run a combat like this where the attackers are on higher ground, and although IMO that should give the attackers a benefit, RAW there is nothing that says you have to expend movement to jump-attack. Anyway, you now have disadvantage on all attack rolls so I think that's enough of a penalty. If you DO want to escape, it will require and action to make a DC 10 STR check, plus another action for Kaylyn to make a DC 14 STR(Athletics) or DEX(Acrobatics) check.

Sekkar STR check : 15

As he freed himself, he did not even bother with the weapon but simply bite his opponent (n10), in hope to bring him  down and take his place on a ledge: Attack: 19 Damage: 10   + Bless: 3 (bonus action, Hungry Jaws)

STR check - 12

Seeing his spell not work, Joetaro is going to attack the enemy in front of him.

Attack: 8 Damage: 7

As a reaction to being netted,  Kastix uses Hellish Rebuke on them.

Dex Saving Throw DC: 15
Hellish Rebuke Damage: 17, half damage on a save

Kastix swipes his hands through the air while speaking, "Let the Inferno take you," and casting Burning Hands trying to catch as many as he can in the attack.

Dex Saving Throw DC: 15
Damage: 7, half damage on a save

Zeno cries out, “They want us to surrender!” He will struggle against the net calling out, “Itxaron! Kuo-toaren laguntza bilatzen dugu!” 

Str Check: 3

Rhayna will try to shield Stool with her body as best as she can.

Can Kaylyn see further up the path that they were following before the attack?  Or saw it before the attack?

Further up the path was more of the same: gully with ledges on either side. You can move through friendly spaces if you wish (unless you are restrained or grappled) to go further ahead, but will provoke opportunity attacks if leaving enemy melee range. Same goes for jumping to empty space on ledge - enemies behind get AoO. 

Knowing that, Zeno will Bonus Action Disengage, then run as far as he can up the tunnel the way they were going.

Quote from Shodai_Kishi >>

As a reaction to being netted,  Kastix uses Hellish Rebuke on them.

Hellish Rebuke is only in response to damage, so can't be used against #5 (net did no damage), but can be used against the spear guy (#14).

Kuo-toa #14: DEX save v Hellish Rebuke: 13 fail 17 fire dmg = DEAD

Seeing that she is grappled she whispers a couple words and she is briefly surrounded by silvery mist, and then teleports 30 feet further up the passage.

BA - Cast Misty Step

Kaylyn then turns back and sends a blast of Eldritch Energy at the one in slot 2 that has a staff.

Attack: 12 + 3 (Bless) Damage: 14

@Joetaro: It takes an action to escape the net, so you can't take Attack action as well. Sorry.

ROUND 2

Rhayna hunkers down under the net to protect Stool and to continue her prayer to Selune. Sekkar fights more furiously, his more primal urges coming to the fore as he rips his way out of the net and bites at the kuo-toa above him. Sarith is bleeding and has lost one sword, so he draws his other and assumes a defensive stance to deflect further blows. Kastix simply stands as best he can inside the net, pokes his arms through the holes and unleashes a sheet of flame at the ambushers, three of whom shield their faces as the flames scorch their scaly hides. Zeno slips out of the net and uses his agility to avoid the spears and kicks around him to flee the scrum, while Jimjar does the exact same thing at the other end. Kaylyn takes a more direct approach to escape by simply teleporting out, and then turns to fire from a safer distance. Joetaro also casts off the net, and stands again to face the foes, while Derendil keeps swinging his claws at the fish-folk, his genteel elven voice urging Joetaro to valiance.

The kuo-toa press their attack as one continues to call out the phrase Errendizio! Seeing that Sekkar and Kastix are the most determined to resist, more of the ambushers turn their attention to them. The two at the top of the column, who seem to be most in charge as well as the most proficient fighters, bite, kick and grab at Sekkar as his back is turned, and finally manage to wear him down. As he collapses to the ground, they order another of their soldiers to tend to the lizardfolk. Aita sakonak odol bizia behar du, they say. Despite Sarith's efforts to repel them, he too is brought down. Three others battle with the net-bound Kastix, but despite scoring several hits with their spears, Kastix refuses to drop. The two chief kuo-toa at the bottom of the column focus on Joetaro, but by Selune's might the paladin resists their attacks, although another net falls on him.

Sekkar and Sarith are unconscious.
Rhayna, Kastix and Joetaro are restrained.
Kastix, Kaylyn and Joetaro are under the effects of Bless.

 A map of current positions. Each cell is a 5'x5' square. #15 and #7 still have a net. #7 and #8 are asleep. 

 Kastix casts shield as his reaction to stop the attacks from hitting.

Rhayna sees that her companions are fighting their way out of this ambush, she joins the fight. Still holding onto Stool with one arm, she looks at the kuo-toa that tried to stab her with its spear (#15), raises her other arm through the net, and casts Toll the Dead on it. (WIS 14, DMG: 5)

(OCC: Sorry, it has been crazy at work.)