Unless you hear popping of whistling noises I would not be too concerned about the "crust" probably just a little stuck shed.

The other thin remark...pet stores often only feed the bare minimum so they can turn a profit, so it's probably just a case of needing to be fed regularly.

Are your temps good, humidity? You know how much and what to feed it right?
Just basic common questions to see if their could be any other problems.