I wouldn't start to worry too much yet. Just keep an eye on his weight. Also has he pooped at all since you've had him? Thats usually a good indicator if something is up or not. If he hasnt pooped yet then he might still be digesting, or just isnt hungry yet. I have a male who hasn't eaten since September but fluctuates between the same 50-60g, another male about the same weight as yours hasn't taken a meal since December. Try more hides and offering every two weeks rather then every 5-7 days so he's not as stressed out maybe? Good luck.