My hair grew back with no extra anything other than VitaLady's vites and a lot of protein. I drank 2-3 shakes a day and ate a lot of protein and my labs show that I am absorbing a lot of protein.
I have always used a lot of splenda and use it more than ever now.
What are your labs like? How much protein do you get? Do you do shakes? That is where I would start if I was having a lack of return of hair.
If those are all really good then I'm at a loss. But I doubt if stopping splenda is going to do it.