IMHO you need to go back to the doctor or to a new one. Take pictures with you. Also mention that others have also noticed and are concerned. I know you've had blood work done, but I think it is worth looking in to again. They probably didn't rule out all possible causes with one blood draw. The squeaky wheel gets the grease, right? Hair loss can be normal for woman, but not at your age. There are many causes that can be reversed.
Here is what I know from what I have read. Hair products aren't going to make your hair fall out. If things went bad (think very bad color) your hair could break, but it won't fall out. Hair products also won't make your hair grow. Vitamins won't make it grow either, unless you have a vitamin deficiency.
I hope you find the answer.
I'm not familiar with any of your products. I do know deva stuff gets mixed reviews here. None of it really has a huge following.
http://pedaheh.blogspot.com/ (a blog to help new wavies, go to the how do I get started page)
2a (nc.com) 2bFi (Fia), very fine, thin, low/normal elasticity, porous, CG, doesn't get weighed down
Cowash: Tresemme naturals
Rinse out/leave in: Renpure Organics (red)
Curl enhancer: FSG
Gel: BRHG, Salon care aloe, Ecostyler Krystal (normal dews)
PT: ION effective care, IAgirl's gelatin PT
Low Poo: renpure (red), Ion swimmers