Sometimes they will get tired of a food item. That's why it is recommended to give a variety of feeders. I usually rotate between crickets and silkworms, with the occasional superworm. If you search the threads for "hunger strike" you'll find that sometimes a cham will totally refuse one type of food. Then you have to find something they like.
If your cham is down at the roots of the plant digging around, it could be a sign of lack of supplements. Sometimes they eat dirt if they are trying to get some nutrient. What supplements and schedule are you using, specifically?