I've had my Platys for 2 months and recently one of my males has stopped eating and stays still at the back of the tank behind the filter output with heavy breathing. He also has white/clear faeces that are much thicker than normal. The other 7 platies in my tank seem healthy and are very active.
This all comes soon after adding some new plants to the aquarium and switching to a new filter (I did add the older filter media to the new one without letting it dry out). Current water conditions are: 0.25 ppm
Ammonia, 0 Nitrites and 10-20 ppm
Nitrates, I'm currently performing 35% water changes twice a week until the new filter catches up.
On advice from my LFS
I'm dosing with this stuff: https://www.ntlabs.co.uk/browse-prod...-fluke-wormer/
Although I'm skeptical if this is the correct treatment as I didn't think worms or flukes caused a loss of appatite.
The pictures below are of the sick platy. He has some dark marks on his head near his gills too, I can't remember if these were there before and all the other orange platies have the same marks so I'm unsure if I should worry about them or not.