Hmm... You are supplementing and gutloading.... How old is your UVB bulb?
I'm not experienced with veiled chams, so you might check the care sheets here to double check basking temps and etc.
Just in general, ditch the flukers stuff with calcium. Everyone says it's junk. Get a better engineered gutload like cricket crack or bug burger and keep giving fresh veggies.
Do you offer anything besides crickets? You might be able to get calciworms at a local pet store - very high in calcium. Silkworms, hornworms, and super worms are all good to rotate into his diet.
As for being dark and crabby, it could be a general sign that he is not feeling well. Does he bask all the time? If not, he's probably not cold.