This sounds a lot like my daughter, who has issues with food as well. She's not as bad now--she's 10--but when she was little, there were only 2 to 3 foods she'd eat. She has issues with taste and texture and spice (doesn't like spicy foods, or any added flavor, for that matter. She likes bland.).
Our issue now is to train her to eat or at least try the food her mother and father are eating, so we don't have to continue making two separate meals. Even when she didn't/wouldn't eat when she was younger, she had to sit at the table with us. We never had meltdowns to deal with, though. We just had the issue of not being able to get her to eat unless it was food she liked--and made the way she liked it.
When she was 5 years old, we found out she has Sensory Processing Disorder, on the high-functioning end of the Autism Spectrum. Food issues is one of the areas, as are bright lights, loud noises, and social situations. Not saying this is your daughter's issue, but it was the first thing that popped into my mind when I read about your issue. My daughter was bottlefed and ate anything and everything until she was about 1.5/ 2 years old but after that, it was like a switch was hit and suddenly, what she would eat was drastically reduced.
We also switched our household over to all organic food about two years ago, as it was discovered that my daughter had severe heavy metal toxicity and has mild gluten intolerance. We've also noticed that since we quit using cow dairy products (my husband and I found out we have a casein allergy), she's been doing a lot better (less anxiety and less meltdowns/frustrations).
You might also want to have your daughter seen by a naturopathic doctor to be checked for heavy metal poisoning and food allergies/intolerances. Do some Internet searching on Sensory Processing Disorder as well; there are lots and lots of different areas--visual, hearing, seeing, taste, spatial/movement (my daughter has this one as well, and has issues with riding a bike and coordination (she takes dance for that) as well as hypotonia, low muscle mass) that your daughter might fall into, besides the area of food. I have a friend whose daughter has refused to eat since she was a baby, to include breastfeeding and/or bottle and/or solid food, and they eventually had to put in a feeding tube. They even went through intense training on how to "relearn" her to eat. I don't know how she's doing, though. It's been tough on the family, so I know what you're going through. And it is very apparent that your daughter isn't eating enough food or getting enough nutrients to feed her growing body.
Visit Dr. Lucy Jane Miller, PhD, OTR, Web site for more information on Sensory Processing Disorder: www.sensationalkids.org. She is a pioneer in this area. I have sent them many e-mails asking for help with my own daughter, and they have been very helpful.