My daughter isn’t gaining weight fast enough

HELP! What are some fatty foods I should give my daughter she’ll be 10 months on the 30th but she’s barely 13.12 pounds. She’s had weight issues since she was born. Her doctor wasn’t concerned about her weight because she’s developing just fine and meeting milestones perfectly. But I need help with her weight gain she takes a bottle every 3 hours but she only drinks 3-4 oz and she eat everything under the sun just fine but no weight gain idk what to do! What are some foods that will help her gain some weight