I've had two geckos shed this past week and both exhibited the same problem during their shed. It seemed like all of their skin would begin to shed except the skin on their head, which would be delayed by about 12 hours. The end result being that the skin on the body was successfully shed, but on the head the skin would be stuck and/or hanging in little pieces. Could this be a sign of some nutrient deficiency? (I do feed with calcium w/ D3 and Herptivite)