another possibility is brumation, it is that time of year again. How much has he/she eaten overall since you got it? is it spending a lot of time on the cool side of the tank and/or sleeping a lot? is it noticeably losing weight at all?
Probably relocation stress to be honest, most beardies during their first couple of weeks at a home will not eat as much while they adjust. Also some beardies really dont like greens all that much. Just offer them and let them pick if they dont eat well they dont eat. I wouldnt worry about it...