Personally, I wouldn't touch soy formula if you paid me. I would go the goats milk instead. decades ago many babies who couldn't tolerate cow's milk did perfectly well once on goats milk and I have an issue with 'milk' that comes from plants kwim? It's just not natural.

It does sound like there could be an intollerance there, but it could just be the reflux too. You really need to see the pead to get to the bottom of this as a GP just wouldn't have the specialised skills kwim?

Don't worry about her weight for now though, and alone it wouldn't be a huge issue, but combined with all the other things you are right to be on 'alert', but I'm sure it's nothing that bad that it can't be dealt with easy enough too OK? It's tough on us Mummies when we just can't figure out what's going on.