4 week old has diarrhea

My baby is 4 weeks today. We have been having reflux issues so I had switched her formula to a soy, which seemed to help but then caused constipation. so her pediatrician said switch to enfamil nuro pro infant formula, fill a prescription for Prilosec (which can take 2-4 weeks to kick in for reflux to improve) and add one oz of prune juice to ONE bottle a day. I’ve been doing that since Monday, she is still struggling to poop sometimes. But I just had to change her twice in the matter of 20 minutes due to straight liquid poops, and she kept going mid change. Should I be concerned that it is diarrhea or is that normal since she is using the prune juice? Ftm obviously!!