Fish died unsure why

Hi I noticed my platy was on the floor in my main tank very odd for her. She's been in a small tank alone for about a week where I notice she had a small pop eye, she's barely been swimming and barely eating. Definitely not been eating last few days and looks skinny I've tried treating her over the week but nothing had perked her up is there anything I may have missed based on her appearance? She passed today. I've been doing 25 to 50 percent water changes daily over the week and main tank parameters I've checked using my own testing kit.


Unsure of age had her for only a year or 2 from pets at home she's had lots and lots of babies over summer and then stopped