clownfish poorly

Hi I woken up this morning and my clownfish is not doing ok I had him for around 3 months and about 1 week ago he had white poo so I treated him for parasites and worms and now he sudden taking a turn overnight I have check the water everything is perfect my other clown is doing is doing...

I have a poorly clown fish and poorly mandarin. We are suspecting fin rot, can anyone confirm? Both are very lathergic, Clown is still eating, mandarin not really moving. Both seem to be struggling to breathe, laying on the bottom on the tank appearing lifeless :( Not managed to get a good photo...