I’m sorry to hear about your issue getting to eat. I’m just seeing this thread but If you haven’t yet, Try nightcrawlers, I’ve noticed my most stubborn rays won’t touch bloodworms or any other type of worm other than big Canadien nightcrawlers. Cut them up into appropriate pieces like others have said
If you want to try medicating then I myself would be deworming using prazi. Then I’d wait and see if they ate and if no luck still after a few days then I’d treat for bacterial with nitrofurazone