i had a Bandit get that cotton-like stuff on his mouth .. he ended up passing away within a couple of days i saw one of my Juliis, who is huge, swim hard and fast at him, and i think he pierced the Bandit, allowing an infection to take place ...
i treated the whole tank (30 gallon) with salt and nobody else (14 other Corys, 4 guppies and 1 BN pleco) got it.
i have every medication known to fish mom and dads (because i just know the day i really need something, it’ll be at 1 am and nobody will be open) yet i always turn to salt first.
good luck and hope your little guys make it. ♥️