My middle child was never a good eater. As early as breast-feeding, if she were distracted, it was the end of meal. She seemed not to like food at all. She would not even eat a strawberry or banana. She literally lived on quantities a bird might eat.
She did however, eat sand like crazy and enjoyed treats like catfood. Lack of minerals?
From ages 4 - 7, she seemed to be on a white diet - mashed potatoes, rice, bread and pizza (but never my home-made pizza). Even at McDonald's I would order her a plain hamburger- hold the meat.
Since I realized very early that eating was not her strong suit... and I worried that battles at the dinner table would someday turn into anorexia... I simply offered the food, but never tried to force eating.
The child is a lovely 21 year old now - that still eats very little but binges on what she loves.
My youngest child was always over the 90th percentile for weight. Doctors insisted he must be put on a diet. I felt that he was a big boy with big bones. I always let him eat as much as he liked. He is 17 now, and at 6'2", he fairly recently thinned down to the perfect size.
I have had endless bad experiences with doctors. I have much better results with home remedies. Nurse practitioners are wonderful when medical help is really needed - which is rare.
One of my favorite coping sayings is, "If the child [isn't doing it] by high school graduation, I will worry about it then. Each child matures at their own rate, so don't worry about what everyone else says. [Insert whatever you like in the brackets - potty training, sharing, flushing the toilet....]
Also, I do not recommend stress. I stressed with my oldest child a few times when she walked beyond my reach. How she loved the fear on my face. She became so adept at disappearing whenever I did not have her in a wrist lock. In stores, she would hit the floor, roll under a clothing rack.... I once had the entire staff of JC Penny's walking across the store in a straight line as we beat the clothing racks to find the child that loved to stress-out mommy.
(This child grew to be very independant, a natural leader, and great scholar.)
I have seen some real disasters from over-controlling parents!!!
I suspect I have a similar make-up to your daughter's. I joke that sleeping has never been my strong suit. I grew up eating very little and being extremely active. I was always climbing trees, jumping creeks, riding bikes, swimming... Eventually, I put myself through college on athletic scholarship (while working and taking full care of my horse, graduating early with a BS in Psych and minors in Animal Biology and Computer Science....) No one bothered to test me. All your daughter's tests are normal. I have no doubt you will seek medical attention when it is needed.
You are obviously a wonderful parent. Relax and enjoy the early years. Be sure to laugh out loud daily.