I don't think it's too concerning since he is still a good weight. In the pictures he looks a little bit dehydrated, I'm not sure if you have a way to increase humidity or not (like covering the lid if it already isn't or misting more often). For food I also recommend Pangea, it's best to give a variety of flavors. Feeding insects is also important for crested geckos (usually 2-3 times a week). Most people feed crickets (I recommend putting a carrot in the enclosure to avoid injuries) but I personally use dubias. For insects try to avoid harder bodied insects (mealworms and superworms) and BSFL (crested geckos have trouble digesting them).