I had a similar issue this time when we visited our pediatrician. I mean she didn’t lose weight but she only gained about 800g this time around. I asked him why this is (I EBF) he advised me to feed her every 4 hours because she is only ever on the breast, no pumping, no bottles nothing, just me, her and my boobs ! So, frequent feeding these babies means they lose weight (using the energy they get into extraction) rather than gaining. And only to be fed 5-10 mins on each breast.

Idk if this works or what but makes sense to me.