Ay, been there with my picky eater din! Para sa healthy weight gain, most of us moms swear by multivitamins with zinc and iron like Enervon or Caltrate kids line, pero honestly the best results I've seen with friends' kids is when combined with consistent nutritious meals, more calorie-dense food like peanut butter, avocado, eggs, and milk products. Better talaga to check with your pedia kung may specific deficiency ba or kung medically underweight siya, kasi ang vitamins ay supplement lang talaga, hindi replacement for good nutrition, and they can recommend the right formulation for your kiddo's age at needs. What's your munchkin's usual diet like?