Have you considered the possibility that you are over-training your quads? Although your workout routine seems good, if it isn't doing for you what you want it to, try something different. I train quads one day/time a week and hams on another day. This works for me, but I am an old man and thus need more recovery time.
I doubt there is a magic pill which specifically works for building legs. If you eat right, get plenty of rest and decide (as you apparently have) to use AAS, use it sensibly because more is not always better. Be careful to not sacrifice your health for the sake of getting big. You could very well end up worse off than if you just trained naturally.