Well...

Everyone notices that small little holes line the walls, little crevices a normal sized person could fit two fingers in. The small holes go deeper than you can reach, and they are oddly uniformed, in straight lines on the walls, forming a grid. 

Artan:

Ember, Flax, & Beshlog:

Ember quietly whispers a Blade Ward.

Stealth 19

Artan, will you act?

Artan will attempt to react quickly to warn Kordia (dex save 14) whispering loudly "Watch your foot!" and attempting to grab her backwards if he is close to her. 

Kordia --  Passive Perception: 14

Acrobatics (( expertise level )) :  23   to twist herself mid step and end up one step backward... almost a pirouette?

(( If that kept Kordia from stepping on 'the spot'... ))   Kordia will give Artan a thumbs up for the warning...

vvv  For Ember, Beshlog, & Flax  vv

Kordia manages to not step on the pressure plate, and dances (literally) back, unscathed. 

What do you do?

Kordia releases a held breath after her near ballet like move to keep from triggering the floor pressure plate.   With a hiss, she indicates with gestures and very low whispers to those not linked to her psychically.

How shall you proceed? Maybe try examining the floor and walls to find a way past.

If it takes investigation, Artan will leave that to someone else as he is not very good at it. But if it requires perception, Artan will gladly try identify a safe path through the corridor.

Rolls for if it is perception:

Kordia frowns as she looks around.  With a nod she invokes Dancing Lights and guides them down close to the floor to highlight any irregularities in the paving stones.

Perception: Dirty 20  {game log}

It seems, under the investigations of several party members, that the triggers are set in such a way that the pressure plates are spread evenly apart, so you would have to step or jump (depending on your height), over each one of them. In total, as far as the party can see, the holes seem to stop about 20ft down the corridor, and with them the pressure plates.

Anyone who wants to cross, make an acrobatics check

Acrobatics 16

Kordia says softly, "Here goes nothing... "        Acrobatics: 30

You said step depending on height. Would the taller ones among us still need to roll? 

Beshlog will wait for everyone else to go first before he tries to cross the gap. Then he begins the treacherous trek.

Acrobatics: 13

Quote from Swiftgale >>

You said step depending on height. Would the taller ones among us still need to roll? 

 That is a very good question... I feel like Beshlog would be tall enough to simply step over the plates without too much issue unless they're REALLY big.

That was intended for the shorter people. But everyone manages to make it across, and you are ready to head into the darkness.

Any special precautions you are taking to avoid something like that happening again?

Artan will be near the front to keep a closer eye out for traps. 

You continue on, and make your way down the dank tunnels. They look very similar to the ones I've been describing, so I won't repeat what I've already said. As you march over a small rise in the tunnel, Flax notices light and noise up ahead, and most of the party can also hear the sounds of strange clicking and clacking, as well as laughter.