It sounds like foremilk/hindmilk imbalance. Try nursing baby only on one side and see if the color turns back to yellow. Too much foremilk (first stage of breastmilk) will lead to green seedy poop.
This happened to us around then too. Our easy fix was letting baby nurse longer on one side - which allowed her to get more hindmilk.
I asked my pediatrician if green poop was a sign of anything and she said it would turn green from quicker than usual digestion. If it's just occasional don't worry.
Re: Green poop
This happened to us around then too. Our easy fix was letting baby nurse longer on one side - which allowed her to get more hindmilk.