Refusing food

So I have had my beardie for a month and love him. He is full grown, and he ha never refused food. Everytime there is crickets around he freaks out chasing them around eating. But these past 2 days he hasn't eaten anything. He has Been sleeping more and his beard is black all the time. He acts like crickets aren't around.
Does anyone have an idea of what could be going on? Nothing has changed in diet or his cage the whole time
Thanks.

A couple things might be going on. You mention that he's full grown which means he doesn't need or want to eat every day. My adult girl eats between every 2 days to a week depending on her mood. Also, some places are cooling down now which will shift them into brumation. They will sleep in a cooler section of the tank and stay there for weeks on end. This happens whether you leave heat on or not and seems to be connected more to outside weather, pressure, light length, etc. They also won't eat or drink for weeks during this time and are just fine. If he's in good body condition, give him a bit and remember that as adults, insects are only needed maybe once per week as they need a higher vegetarian diet once they are full grown. Only the babies need the large amounts of protein. Personally, I use insects as treats about once a month while their staple diet is RepCal that's been soaked along with various greens to munch on.