Illness/Sickness: CFB newt larvae dying quickly

Hello

On Thursday I had 33 tiny newt larvae, up to about 14 days old maybe. Today I have 22. They are dying really quickly, and before this I had lost maybe 2, really new babies. The ones that have been dying have been including what seemed to be strong larvae, some with their back legs appeared even. Whats going on and can I stop it?

I did a water change last night, and changed their containers too, in case it was something to do with that but have come through to 3 dead newts this morning (I lost 8 yesterday). The bodies all look a bit fluffy, are they being killed by a fungal infection? None of the live newts have any signs (that I can see anyway) of any fungus or fluff on them, but they all looked fine last night too. The only thing is that one of the dead ones seemed to have its tail curled a bit last night, just the tip, while it was alive. I am feeding them baby brine shrimp, I was feeding them microworms too but I have stopped now since I was worried about them carrying disease.

Anyone have any idea what is going on and how I can stop it? The older larvae and the adult newts seem fine.

Thanks for any advice.

It's hard to say from just a description, but it sounds similar to the Case History described at the end of this article:
Caudata Culture Articles - Why Larvae Die
If it's not already too late, I'd suggest trying moving them to a clean container of clean water daily.