if your GP isn't worried, then i wouldn't be too worried. fwiw, my DS has cracked 8kg at 4 months (birth weight of 3.99) & was over 10kg at 8 months but then slowed right down because he was crawling & then walking - it was like he stocked up on weight to cope with being an extremely active little person!
i BF my DS so don't know about FF but at 6 months old i wouldn't cut back on milk too much cos it is still meant to be their main source of nutrition for another 6 months.
I think she's doing beautifully! I really dont think she is gaining too much weight. If she was having problems with lactose earlier, then it may have prevented her from gaining as much weight as she was genetically *meant* to gain, but now she is growing as she was meant to be growing and going great guns by the sound of it!
Bookmarks