Dartfish is starting to get white tips on it's dorsal fin and tail fin

[Bonta]

I've noticed that the tip of my Dartfishes tail is white and looks like something bit the tip off leaving white residue behind.
Now the dorsal fin has a white tip but hasn't gotten shorter. Is this fin rot ? If so how did it start and how can I prevent it ?

 

[Bonta]

AGH ! I just read the symptoms of flukes and I'm pretty sure it had them. Discolored spots of skin, stringy poo, and not a very agressive feeding habit as it use to but it still eats.
I read Prazi eliminates this
Should I just dose the whole tank since I'm pretty sure my other livestock are infected. My corals consist of a toadstool, purple mushrooms, and some anthelia. My inverts are just 2 hermits , 2 Narsarius snails, and 1 Turbo.