i usually put Stress Coat on mines. grab them near the top of the water let them stay in the water with the net just holding them in place and add small amounts of stress coat.
Oh i did have an slight ammonia problem so been doing water changes past few days but our tap ph is 8 but the test at the lfs said the water was acidic. Need a bigger net to do stress coat.
Sounds like a pH crash, it killed all ur filter bacteria. Check your water parameters.
Increase O2 and add Seachem Prime which neutralises ammonia n nitrite.