looking at this again, it almost looks like some of their gills are kind of flopping around and some of them look curled, maybe too much water flow for such a small area? also in the last picture it looks like there' a golden who is at least a couple inches smaller than all the others i hope for the best but it doesn't look like a good situation, this many animals in such a small space seems like it's really asking for trouble...
The water is fine, it's being filtered by a sponge filter which is the least disruptive filter there is. They look perfectly healthy and the one that is smaller is totally fine as long as he can't fit into another one's belly which from the looks of it there's no way he could.
Now what I honestly can't stand about this thread is that there are people who are being outright rude to the original poster because they simply didn't know any better... Saying things like that 20 dogs in an apartment jab or the "Why do you have 16 axies in such a tiny tank" even after the person already explained themselves... Really? How about you offer something constructive for them rather than just blame them and accuse them?
Ie: My post about the bath tub, perfectly good place to hold some axolotls until you can get a bigger tank.
Or how about you mention totes? Big totes with a filter, perfect tank for an impromptu animal overload.
Also let's not forget that 10 gallons an axolotl is the bare minimum for the optimum conditions. These axolotls are not going to die as long as the original poster is taking good care of them, being diligent with water changes, feeding them correctly, etc.
I'm not saying it's healthy, good, or even okay conditions, but it isn't life threatening for the time being. They're small enough right now for it to work, hopefully the person will invest in a bigger tank soon.