Good night mommies, I wanted to ask, my daughter will be 15 months old…

Good night mommies, I wanted to ask, my daughter will be 15 months old in two months, she's not strong enough with her hands, that is when you give her your finger she can touch but doesn't hold on, she doesn't want to hold at all. Sometimes she can grab and hold tight sometimes not, well basically it happens once in a while. Should I worry? Or did you have something like this?