Marla sees what Flowers is doing and prepares to flee, in case the fire actually catches and lack of oxygen becomes an issue...

Jorah, hearing the warning, (cunning action) disengages and backs the heck up.

Jen tosses another Fire Bolt at the ooze.

Attack: 18 Damage: 9

And then moves away.

(I am going to describe things based on the initiative order so hold on) 

Flowers tosses his torch towards the stack of matresses. Almost immediatly the fire spreads from one to the other as thick black smoke begins to rise up and spread across the stone ceiling above. The flames don't really have anywhere to go since the floor, walls, and ceiling are all stone but the mattresses start to fall apart and spread out as the fabric holding the straw together burns away. Jen and marla quickly launch their spells seconds before the smoke starts to sting their eyes. Both spells hit and the creature bubbles and twists before collapsing into a sizzling puddle. 

It is rapidly getting hard to see (lightly obscured) as the room fills with smoke. You think if you stay in this room much longer it will get harder to breath and even harder to see.

Flowers looks really proud of his achievement and smartness in dealing with the ooze.

and starts to cough as the smoke gets thicker

Misha smiles and shrugs. That's not what she meant about fire and passion, but..you gotta work with whatcha got. She taps a button on her forearm brace and a slim fitting half face plate covers her mouth like a Covid mask.

Cockroaches and rats flee from the flaming mattresses.. skittering around your feet as smoke continues to fill the room.

"Oh, hello!" Misha waves. "Yes, flee leetle creetures!"

Marla flees back the way the group originally came, on the basis that there are known rooms / exits that way to wait out the fire, which has only got so much fuel, given the aforementioned stones floors, walls etc, and is in the direction of (comparatively) “fresh” air...

’This way everyone, we need to wait away from the fire until it’s extinguished itself...’ she shouts, then mutters under her breath, ‘Idiot cat...’

Flowers will close the door to the flaming room and follow the others with a big smile on his face.

Jorah, seeing the flames rise, pulls out his small pot/bucket and double dashes back to the sewer to fill it with water. He comes back, huffing as he's not very strong.

Flowers will take the bucket from Jorah and toss the water in it on the fire he so gloriously created

[CON save: 5]

Alexa grits her teeth and brushes her fingers across her holy symbol. "Ilmater, grant me strength. A lot of strength," she murmurs, casting resistance on herself before beginning to work on putting out the fire, using her blanket and helping Jorah refill the water bucket to put it out.

After taking the time to head back and collect water to throw on the flames, the fire is extinguished. It takes a few trips and as the flames grow smaller, the smoke grows thicker. The room is now heavily obscured and any creature inside the room (Ending its turn in the room) will have to make a con save or take 1 point of damage from the thick smoke unless you crawl along the floor. 

Alexa does not crawl, focusing on getting the fire out as quickly as possible.

Con ST: 16+1

She will also recast resistance, whispering a prayer to Ilmater among the flames.

Flowers will go through the room and open the non ooze door

Misha follows close behind, making sure nothing else is set on fire.

Marla crawls along the floor, knowing she can fix any tears in her dress and clean up, at the other side...

Alexa is able to brush the smoldering straw and fabric away from the two bodies on the ground. The goblin is dead, its skin is charred and the eyes have seemingly boiled out of its skull.. 6 The baled headed bandit is barley recognizable. The eyeballs tattooed across his scalp have all been charred and peeled away. 

As the group leaves the smoke filled room, they find themselves in a narrow hallway. Making their way south the see flickering lights illuminating the opening to another room at the bottom of a small set of slick stone stairs.

Threadbare curtains hang on the east wall of a long hall-like room, in the middle of which a muscular half-orc in dingy robes stands with his foot on the chest of a male human with wavy red-blond hair. Fire burns around the orc’s clenched fist, and his victim cries and squirms helplessly beneath him.

Seated on a raised platform to the south is a nightmarish figure wearing black robes. It has large white eyes and rubbery purple skin, with four tentacles encircling its inhuman mouth. It cradles and gently caresses what looks like a disembodied brain with feet.

In the fire room: Alexa looks down at the bandit's body for a long moment, hand going to the collar around her neck for a second before she shakes her head and murmurs a brief prayer to Ilmater. The cleric then turns and heads after the rest of the group.

Now: Alexa's eyes narrow, fixing on the orc and glowing gold. A pillar of divine fire slams down onto the floor beside the orc (in a spot where it won't hit the human). "In Ilmater's name, I will give you one chance to cease and surrender, torturer." She says the last word as if it's the absolute worst thing anyone could ever be.