Biogaia drops is good. Normally it help to prevent loss stool and prevent constipations. Reflux might not due to probiotics maybe you want check with your baby doctor to see to add on medication.
My LO had reflux too. I gave LO A.R formula and use dr brown anti colic bottle. She had constipation and dr prescribe priobiotic. But she didnt have diahorrea, her stools were just softer.