Big 99th percentile baby dropping weight (help)

Does anyone have experience with this? My doctor said he wasn’t concerned but wants to ‘monitor’ it so he is obviously worried.

He was born 99th percentile then dropped to 91st and now dropped all the way down to 75th! All in the space of 2 months.

I’m just concerned because I am on demand feeding him (formula) and when he’s hungry I’ll feed him. I’m just doubting myself as a first time mother or thinking there’s something wrong with my baby 😢

If you also had a big baby and this happened please let me know your experience. Thanks!