What wet food are you feeding him? Things like whiskas and Felix only contain 4% meat. Of course it's a personal choice and there's nothing really wrong with these brands but a lot of people on here feed 50% plus. It's possible it's not filling him up. Personally I use Hilife and tesco luxury/tesco finest foods (yes the cats eat better than me lol). The tesco one works out only a little bit dearer than whiskas. Hilife also do a special kitten food.

Is he eating the same biscuits that he was at the rescue? If they are different he may just not be used to them and you could get some of whatever he was eating before and gradually mix the new ones in.

Hope this helps a bit

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