Both of them miss. Stella will use the dodge action and stay by the ladder. 

The unturned skeleton rips out a rib and moves 5ft forward to attack Ada. Attack roll: 21 for 2 damage

Kess' turn

Kess sighs in frustration, stepping back and drawing her longbow. She'd like to do this in a way where no one has to take the skeletal explosions, but doesn't have any way to do it.

Action: longbow to hit on unturned skeleton 9

That misses, Razz's turn.

Ok, Razz will try to hit the unturned Skeletrap as well but will miss.  He will use his bonus action to heal Garrick for 5 hp.

Eldritch Blast: to hit: 9, damage 5

Bonus Action 1d6 (5) Healing Light

Razz looks around and says, "Okay, so we’re all a little shaken—but let’s try aiming for the skeletons and not just their general area"

Garrick lets out a slight chuckle at Razz’s words despite their situation. Laughing in the face of death. He heard the expression before but doubt anyone meant for it to be as literal as this.

Chipper's turn

Chipper takes a look over at the bunched up skeletons. He didn't like how they exploded into shards next to his allies. But perhaps they'd be able to get them from a distance. Pulling out a chip of mica from his component pouch he says to Stella, "Cover your ears, Kitty." And then with a sense of finally he intones, "Kaboom."

Shatter @ skeletons (maximizing number affected)
Damage: 4+2+8 = 14 thunder
CON DC 15 for half damage

We'll assume that hits four of them, including the unturned one. 

Saves: 21, 16, 20, 10; 3 successes

The damaged one dies. Ada needs to make a DC 13 Dex save or take 10 piercing damage, 5 on a success. The other three skeletons are no longer turned. 

Ada's turn.

"Ow, that hurt," Ada grumbles as the skeleton in front of her explodes, sending shards of sharp bones all over her face. 

Deciding to try something a little different, the paladin will back away from the other skeletons and launch a javelin at one of them from range. "Explode at each other," she growls. 

Javelin - 11 to hit, 4 damage

The skeleton makes an opportunity attack as Ada retreats. 15 to hit for 1 damage. The javelin hits, but doesn't kill. 

Garrick's turn.

Garrick now bolstered by their little joke earlier, aims and fires at the skeletons (closest one, then the next closest)

21 to hit for 18 dmg
19 to hit for 21 dmg

Garrick's first attack kills one skeleton, who explodes into the other two. His second shot kills the next skeleton, whose explosion kills the third skeleton. They then explode with no one in range. 

Stella stays near the ladder. The 2 remaining skeletons are both turned.

Kess' turn.

Kess is relieved to see only two skeletons left. She looses an arrow at one.

Bonus Action: Steady Aim

Action: longbow to hit with advantage 19, damage 9+7 sneak attack= 16 piercing 

Kess' shot hits and kills. Its explosion hits the other skeleton.

Razz's turn.

Razz will target the last one standing and says, "Well with that joke last round, here's hoping I can at least hit This one." 

Attack 1: to Hit: 19, Damage 13

Bonus Action: Healing Light 4HP on Garrick

The final skeleton explodes. Stella slowly walks away from the ladder. "Moving bones gone? Good. Little Kitty relieved."

"That's all for now at least. The skeleton in the chest doesn't seem so strange anymore." Kessintra remarks, moving to retrieve an arrow from the bone piles before turning her attention back to the hidden door. She examines it for a lock or further traps.

Investigation: 21

There's no lock or trap of any kind.

Kess tries to open it.