At the end of the day, it's important to remember that you really don't need to catch up. As long as he's being fed appropriately now, that's the best thing you can do for him. Any damage that's done is done, and it's reasonably likely that there's little to none in the first place because snakes are made for low food conditions. It's what they do best. Just let him grow at his pace. Also, he's very cute.