mbuna with a sunken belly

[Savethemall]

Hi, about 2 mounth ago we've noticed her belly being sunken. about 3 weeks ago we changed her food {she was eating meaty ciclids food and now shes eating vegy mbuna food based on algea} and try a treatment with praziquantel.so far no improvment. she is active and feeding, her colors are bit faded but other then that she dosnet show any other symptoms, her poop seems fins as well, short and the color of the food. She is in a 500 L tank alone, temp is 26,WC are 25% every week with air pump and an external filter
im very worried and wanted to ask for advice how to treat her.
thank you

 

[kno4te]

Post ur water parameters. Try feeding some hex shield since there’s an appetite.

 

[Savethemall]

0,0,5-10

 

[A201]

Looks like the YL's tail & anal fin might be encrusted with Lymphocystis. I think she's battling the virus.