13 month old not gaining much weight 😕

I’m mostly vegan. So I cook that way but sometimes I’ll make meat for my kids and husband. Both my kids have a sensitivity to dairy so I either really limit it or don’t use it. In the last 3 months my daughters barely gained anything so the dr was concerned. They had me put her on protein drinks to which I picked a plant based vegan one. I’ve been trying to pick foods with more protein and such. I thought I was loading her up so much. She poops constantly. Well we had a weight checkup and SAME THING. She hasn’t gained much of anything. They are giving it one more month. She told me to try more carby foods like bread and pasta. I’m just not sure what to think. Everything I give her should be meeting the requirements for her age. I also discovered the granola bars and protein drink have lots of fiber, thus all the poop. Next step would be bloodwork to see if somethings wrong. She is super active and I breastfed her up untill 12 months. Any advice?