I have some jeweled lacertas (lacerta lapidus) that I bought about a year ago. They were about 4-6 inches long, including their tails, when I got them. I've raised them under UV lights, varied their insect intake, provided vits/calcium, etc. Not long ago, I noticed one of them acting abnormally. He looks ok, but when I put feed in, he swings his head, seemingly uncontrolably, in trying to catch the insects. It bobs up and down, and swings side to side (imagine a drunk lizard...). The female in there with him was fine, though. But, yesterday, I've noticed she's doing the same now. I've got two others in separate enclousures, and they are fine (so far). Anyone have any idea what is causing this and how to correct it, if possible? Their stools appear normal, no abnormal discharges or other signs of disease.
Thanks!!!

