Fast fading on bottom 1/2 of hair

Last year I decided to go to a reddishy brown from my years of bleach blonde hair!! I've recently gone back to blonde cause I've had the same fading problem! It sucks!! I found that Clairol Beautiful Collections Semi seemed to stick the best in my hair and after I dyed it I would put Warm Brown Protein filer in my hair and also use a brown shampoo & add the filler to that sometimes to keep the color lasting longer. They have a filler called Red Red. It's great stuff and I find it works better on dry hair then it does on wet hair. Also the Clairol Soy and Clairol Complements line has color intensifiers that work really well! Also use a non sulfrate shampoo and don't wash your hair if it doesn't need it just condition. Reds are the fastest fading color. Also I noticed when I had dyed my hair darker then I wanted it it would fade to the color I really wanted. Good luck try the filler first!