Could my child's weight be normal for her

My daughter was diagnosed with FTT at 1 year. She was put on tube feeds at 18 months after failed attempts to fatten her up with food. She likes to eat and takes in about 1400 calories a day, at least. She was treated for a rare cancer called rhabdomyosarcoma and continued her tube feeds while on treatment. However, even with consistent feeds for over 2 years, she never seemed to put on weight. She has been free of cancer for six months and off tube feeds. She eats better than ever and still can't gain weight. What could be going on here? We are frustrated at the lack of answers, and our daughter has been through a litany of GI and  genetic screenings. Our oncologist says the chemo effects should not be causing this lack of weight gain. She consumes as many calories off the tube feeds as she did on b/c now she eats much more during the day. We don't know what to do from here.

[Renee Radenberg]

Both her weight and height are just below the 5th percentile for her age. She has been through a lot for her young age. Based on her weight / age, she should be consuming approximately 1600-1800 calories per day as recommended the following: Fruits (limit fruit juices) = 1.5 cups; Vegetables 2.5 cups; Grains (cereals, breads) = 6oz equivalents; Meat & beans = 5oz equivalents; Dairy products (milk, yogurt) = 3 cups; Oils = 5 tsp; Additional calories to be used discretionary = 195. This food needs to be divided up between 3 meals and snacks between meals daily. Suggest replacing her milk with Pediasure, milkshakes (milk and ice cream blended), or yogurt smoothies (yogurt, ice cream, and frozen fruit blended) for additional calories and protein for weight gain. Hoped this helped.