Needless to say, but I'd recommend getting another scale, whenever you get the chance. If your right about his weight than he should still be good with the weaned your giving him. You can try offering every 5 days until he gets to be closer to 500g, if you want him to put on weight a little faster.

The sun can definately alter a snakes appearance, for better or worse. Was the middle of the day when I got pictures of Joe, and in a few shots he came out looking almost black.