2 month old losing weight - need perspective

Hello - As the title says, I have an 8 week old who has lost weight this last week, almost 100grams. She has been a slow gainer since birth but never lost before. We switched her to a rice based formula a week ago due to suspected CMPA or CMPI under guidance from GP (my milk never came in following traumatic birth, haemorrhaging etc) I’m not seeking medical advice and we have seen the paediatrician and implemented some things already but I want to know if anyone else has experienced this and if it got better!? Also what the underlying cause was? Just need positive stories and hoping to avoid any serious intervention like tube feeding etc