Baby lost weight at 2 month check up

We just went in for our 2 months check up (born 12/29/20) and our babe lost 2 oz and is down to the third percentile... she weighs 8 lbs 15 oz now and at one month was 9lbs 1 oz. at her one month check up the doctor was concerned she gained too much from birth! 6 12oz at birth.. I feel like we can’t win!

she is breast fed and spits up a lot, so I’m not sure if that’s the cause.

The lactation consultant seems to think there is an issue with my milk and she is getting to much fore milk which is causing her to get to much then spit up.

I’m not opposed to using formula because of course I want her to gain weight and grow!!

Has anyone experienced something like this with their little one?? Did anything help?