Small poop balls

My month old son has had two diapers the past two days with small poop balls. Hes never had this before they either have been mushy or hard but never small poop balls. He hasnt had any other poops in the past two days either. Should I be concerned? They are still yellow and no blood. I started giving him one gas drop a day about two weeks ago when the doctor suggested gas drops bc he would only poop hard poops because hes on formula.. And it was working now hes pooping small poop balls.