Went from the top of the growth curve to the bottom

Hi everyone! My son just turned 9 months so figured I’d ask this question to those of you who have a LO the same age. All through my pregnancy and when he was born he was measuring in the top percentile. 96% at birth. We had some issues with breastfeeding in the beginning so his weight did level out. I figured once we start solid it’d shoot right back up. But he’s still a really slow grower! He is now in the 10%. I feel like that’s a really big jump. His doctor says he looks healthy and everything is great but I wanted to see if anyone has experience with this. I just don’t want to be missing signs or anything. He did have a murmur when he was born that closed and the doctor says it isn’t anything to be concerned about. But the slow weight gain coupled with that just worry me a little.