I put a semi permanent light brown over my blonde highlight (t bar) and it came out nice but since doing that the dye has faded a lot (this was about nearly 3 weeks ago that I dyed it) and it's back to being blonde on top and dark hair underneath, which I was trying to get rid of. How long should I wait before using a permanent dye? I don't want to ruin my hair, it's curly and dry enough as it is :(