rogge....Yer gonna be in a world of hurt here in short order with what you have just described!!
You talking about all these flourish products has me a lil worried to be quite frank! With all the chemicals your fixin to throw in this 50G tank, where do the discus fit in? Sounds like you are hell bent on growing a butt load of plants instead of discus. With 4wpg over that 50G of yours, yer gonna need an EI dosing regime, and a whole hella of alot of plants to dose!! With that lighting, you will need to pack your tank full of plants and dose accordingly.
Now this bein a Discus forum...Do you think thats fair for the discus?