Day 1

The markers on the map reflect floor sections that you have investigated and found them to fragile you could crash that floor - this will require no skill checks. I will tell you even more - should you crash the floor you will see 10 ft deep spiked pit.

RAW: Long Jump. When you make a Long Jump, you cover a number of feet up to your Strength score if you move at least 10 feet on foot immediately before the jump. When you make a standing Long Jump, you can leap only half that distance.
Note: the spikes you see at the bottom are not too dense, one may be able to carefully move through the without taking any damage, falling down there is what makes it it scary.
OK, let me help you there - if anyone have a rope you would be able to get down into the pit without problem, going up though would require athletics check. Jumping over may be a better idea, assuming there is no other traps on the other side, which you were not able ti investigate yet.

Bubbles Anguis Strength is 16, right? So you could jump up to 8 ft. I assume that your "investigation" caused floor to collapse and you see that the pit is about 5 feet and you could indeed jump it over.
Now about "see" - as I mentioned everything is covered in dust here and it is hard to "see" anything without "investigation" from the distance of a touch. Anguis passive perception is below 10 however, so you need a close investigation of a floor to figure out if it is a trap even in the light. Elrond who were following you probably spot something suspicious on the other side of the pit, but too late.

Bubbles, if you fail DC 15 athletics check that means you either jump too far or make a step to stop your jump momentum and fall into the next pit unless you safe DC15 DEX save. So if you do less than 15 on Athletics, please roll dex save immediately after

Bubbles, you gain inspiration for stubborn bravery, but also piercing damage as