fishes in very bad shape, black mouth disease ?

hello
i have a 2 fishes that appear to be badly sick

their "lips" have dramatically increased and is black
it seems like it's a disease like plague was to human
i really don't know what it is it's the first time i see such a thing
i really don't know what to do since it for sure contagious !
last thing i want to say those fishes are really sick and
weak .it's seems like they are losing pieces of flesh from their mouth.

Please help!
Kind regards