Moved from Health forum so it would get the attention it needs
The Megaray, as you know, is a real good MVB. What size tank is he in? Does he ever go near the Megaray or is he just laying on the bottom away from it? What is the temp where he lays most often? I'm not sure what you meant by "I use a simple room thermometer I bought at WalMart." There are actually only 2 ways to get accurate readings and that is with either an infrared temperature gun or a digital thermometer with a long wire & probe end. If you're not using either of those, your temps can be off by as much as 20 degrees. Walmart has an AcuRite brand digital with probe for about $12.00 that will give you both basking & cool side temps at the same time as well as a humidity readout. Here is a picture of it and you should find it in the area where the plastic outdoor thermometers are sold. It's a great investment and it's critical that you have accurate temps especially since you are using a MVB. Those bulbs throw out a LOT of heat and can cause rapid dehydration if the temps are too high.
It sounds like his diarrhea has been going on for quite some time. If you haven't been
bathing him & only misting him, he has to be very dehydrated. So, a thorough soaking in warm water tested by the inside of your wrist (should feel warm but not hot or cold) should be done
asap and doing that at least twice a day for about 15 to 20 minutes each time would help to slowly rehydrate him. Also giving diluted Pedialyte (3 parts water to 1 part Pedialtye) by needle-less syringe or plastic medicine dropper by putting drops on his nose for him to lick off will help raise his electrolytes that are also depleted when having diarrhea.
All the vegetables that you mentioned you are feeding, shouldn't be fed very often. The kale and carrots have high Vit A and oxalates and should only be fed occasionally, the green beans, broccoli and corn should only be fed
rarely because they all have high oxalates and the broccoli also has high vitamin C. High oxalates deplete the calcium intake and a high vitamin content in any of them can cause a vitamin toxicity. I recommend that you take a look at this site, it has the best greens/veggies in green print:
http://www.beautifuldragons.503xtreme.com/Nutrition.html Feeding greens like collards, endive, escarole, turnip & mustard greens would be much better and safer for him. Squash is also very good.
Are you feeding live crickets, canned or frozen? Live crickets are much healthier. If you weren't giving a probiotic during the antibiotic treatment, giving one now would help restore the good gut flora that the antibiotics kill off. Soy yogurt (non-dairy), Acidophilus, Benebac are all probiotics that would help with that.
Even though you've been feeding and doing things the same way for months, since he developed the parasites, it compromised his immune system which is making him more vulnerable to all sorts of health issues. I would recommend making immediate changes in his feeding and
hydration as well as filling us in on your thermometer so that we can try to get him healthy. Getting another fecal checked would be a good idea and the vet would be able to check his diarrhea sample for parasites.