Typically when I had one not eat for a while it would then start smashing good like it's no tomorrow instead of just little bits
In my experience they don't graze at all, maybe the first day or two after illness or stress they may only eat a bit, but it usually doesn't take them long to get to their regular appetite, which is vacuum mode. $100 a week is a stiff bill man, those are the kind of expenses people new to the hobby (not you obviously) never take into account when they start caring for monsters or fish worth more than $10.
I just saw this thread. Man that rays is in bad shape. May be to far gone. Do you still have meds in the tank? How often you doing water changes? What kind of meds?
If it affected your CB pup are you sure the tank parameters are perfect? Might not hurt to make sure your not having ph fluctuations or the meds didn't mess with bio! I'm not saying your tank isn't perfect but make sure!!
Kee water clean by small daily h20 changes.
I hope it makes it!
Keep at it its all you can do!
Once mine ate goast shrimp it also started eating worms. I used the goast shrimp just long enough to make sure it was eating something else.