Pygmaeus bloated

[Banjo Cat]

One of my Pygmaeus was bloated noticed going to surface a few times. The following day found it dead floating. Is it possible it ate too much? Also noticed another one bloated.

[Tetranerd]

What are you feeding them?

[Banjo Cat]

Mico worms, pellets for Cory and bottom feeders Kens fish, and crushed flake. Had 9 down to 4.
Parameters 0 nitrite, 0 ammonia,
20 ppm nitrate. My water ph is hard 7.8 I am doing water changes twice a week I use Seachem Safe for dechlorinator.
Thanks for your reply