I have a sunrise platy (who doesn't appear sick) which has had white like fluff to length of base of tail fin for approx 3 months and has not responded to treatment: melafix, primafix and most recently 4 weeks treatment with interpret treatment anti fungus and finrot. Another platy has now started developing it on the upper body fin and fins appear to be fraying and not herself. Has anybody got any ideas for successful treatment and what it is?.