Larvae dying with shriveled gills?

My larvae seem to be eating, growing and doing well but in the last 2 days i have had a larva who appeared to have curled/ shriveled gills (hard to tell exactly what was wrong, but the gills looked shorter. These guys were only about 5 days old, so still very small) anyways, i separated him into another container to watch him because i thought perhaps he was getting bitten by Another larva. Within 24 hours his tail had shriveled into an awkward. Twisted s shape, his body was contorted and shriveled and he was dead. The same thing happened thr next day to another larva.... Does anyone know what causes this? I had heard that normally when larvae die they become bloated and float to the top, but that wasnt the case here. He shriveled up. Could this be from a fungus? The other larvae are fine so i dont think its the water quality. I use aged water to remove the chlorine and thenqater temperature is about 60 degrees. I do regular water changes ans feedings with baby brine shrimp.

If it is from a fungus, what's the best thing to do at that point?

I doubt its fungus. Fungus would usually appear on the dead Axolotls if they are left in the water for too long.

Not all larvae are viable, some just don't make it. There are a lot of factors that could cause the death, its usually a genetic issue, or poor water quality.

You should use a dechlorinator to guarantee your water is free from chlorine, chloramine, or any metal toxins. Tetra Aqua Safe, Fluval Water Conditioner, or Seachem Prime are some of the most reputable.

When you feed the BBS, when do you do water changes? How much and how often?

Dang thats a bummer. Ok. I am using the dechlorinator now. Just before i feed the axolotls, i take out most of the water and then add in more fresh water and the baby brine shrimp. Then i change it again after they eat.

Would cold water temperatures ever cause a problem for then? I'm wondering if maybe I'm feeding them too much considering that that water is about 60 degrees? I've heard there metabolism slows down in cold temperatures right?

When cleaning out the tank that had all of the casualties, I noticed some white fungi looking growth on the plants. Could a white plant fungus have killed them?

To clarify, after the one axolotl larva died, 5 more died from his tank (which was all of them in that tank). When cleaning out the tank i noticed the growth on the plants

My thought is, either, it is bacterial/viral, or it has a common cause with what caused the fungus-looking stuff, but that it isn't the fungus-looking stuff directly.

Assume it is bacterial/viral, and sterilize everything associated with that tank, and hope it hasn't spread.

I seem to recall reading about something similar with another salamander species (not the fungus-like stuff, but the 100% mortality in a container) but I can't remember buzz-words to find it again. In that case (if I recall correctly), the keeper lost two containers of hatchlings, but successfully treated the third with antibiotics.

Hopefully, one of the more experienced keepers will be able to draw more-firm conclusions and make better recommendations..