normal poop? really need help!

I have a breast fed three week old who supplements formula every once and a while. She also has reflux, not really bad but still spits up often enough. Well she's started to have really watery poop. Like sheer water. It's yellow like it's always been but not even a little seedy like it used to be. Is this normal for primarily brest fed babies to have have liquid poop? She poos once sometimes twice a day so it isn't excessive amount of times.