Hello everyone!

I have 4 cory cats in my tank (they're soo cute!) and one of them just isn't growing. I'm not sure if it's species specific or if someting is wrong. Anyways he's about half an inch and brownish grey with little speckles all over. I bough him at the same time ad an albino a few months ago and they were the same size then, now the albino is twice as big as my little speckled cutie. Is he ok?