400+ grams for an almost two year old snake is alittle skinny..try offering acouple of items a feeding or try and feed them every 5 days. Bumping up the prey size will help as well..Just to give you an idea of how much they can nary though I have 4 month old snakes sitting at almost 300 grams and animals that are 18 months old at almost 1000 grams, then on the other end I have a 2006 female that is olny 900 grams.