EBF baby boy gaining weight slow..

My son was born 6lbs5oz.. when we left the hospital he weighed 5lbs11oz. I went in for his one month check up and he weighs 7lbs now. His doctor said that he’s gained but has dropped percentiles and hasn’t been gaining weight at the rate she would like. She told me to add an extra feeding. He eats between 7-10 times a day for about 15-20mins every feeding from both boobs and he has plenty of wet and poop diapers a day. Should I be worried that he’s gaining weight slow? My daughter was the same way she was 6lbs2oz when she was born and was always in the lower percentile in weight.. I was able to breastfeed her until she was 22 months.. she’s going to be turning 2 next week and she only weighs 22lbs but she is perfectly healthy, just a petite little thing! I feel like that’ll be the same situation for my son too but want to know if I should start taking something that’ll help with his weight gain or should I just continue doing what I’m doing? Also are weight charts for breastfeed babies different from formula feed babies?