Did I switch my cat over to adult food too soon?

So basically I got a kitten from a shelter. He was only about 8-9 months old but he was getting really chunky because he got neutered really young, so he wasn't growing anymore. I put him on 1 cup of food a day and switched to adult cat food without really thinking too hard about it. I was worried he was going to be overweight and unhealthy. However he has been meowing a lot and really unhappy about it. I thought maybe he was just food insecure because they found him without a mom really young (2 weeks). But now Im really worried it's been bad for his brain. He's about 10 months now, should I switch him back to kitten food? I feel so guilty about it if I'm doing the wrong thing. He is still a healthy weight. Edit: So I will definitely be switching him back to kitten food for the last couple months of his baby years but I will still appreciate any advice or any opinions on the matter.