Any redness to the greyish spot on the tail, like a circling or red on the outside of the spot.
Just want to make sure it dosnt resemble a cauliflower.
Forget the maracyn its not working how long have you been using maracyn on the fish.
Any white stands coming out of the spot.
It doesn't looks like columnaris to me (as far as I read about it).
Does it look like it ? No cauliflower or flufy or anything reed (blood) just color changed.
I'll try tetracycline after a week break (with betafix) and I'll let you know.
Many thanks to everybody.