Digestion problems???

A few months ago I rescued a male beardie from a neighbor who apparently abandoned him in her apartment when she moved. He was very aggressive and thin but since then I've managed to get some meat back on his bones and he's looking a lot better than when we first got him the only issue it I recently noticed that his poop has been very runny and the worms I feed him (wax and silks) have been completely undigested in his excrement.
Besides the worms, I also feed him Rep-Cal's adult bearded dragon food, collard/mustard/turnip greens, wheat grass, butternut squash, spinach, and shredded carrots on a regular basis. I don't think there's any intestinal parasites involved because I haven't found any foreign bugs in his poop either.
Does anyone have any ideas of what may be causing this?

Does he have access to correct temps basking in particular? That would be my first guess and the easy fix too boot. Missing bacteria can as well if there were antibiotics used in the recient past. Benabac reptile I found to help recovery of ill dragons. It maybe something to investigate if the temps are correct.

The basking spot in his tank is about 100 degrees during the day and it drops to around 70 at night.
He was indeed on antibiotics for a brief period (about two weeks I think) when we first got him to treat an abscess. I may try to go get some of this Benabac stuff then, where can you buy it?

Acidophiliz+ is good too
http://www.beautifuldragons.com/Acid.html

I would strongly recommend getting either some crickets or dubias into him. Worms are great supplements but aren't good primary feeders.

I would suggest getting hims some crickets and dusting them with calcium and a vitamin supplement, also make sure he has good access to UVB lighting to absorb the calcium and vitamins. Good Luck to you and he's lucky you rescued him.