Nutrients too low. Dosing KNO3

[cflow]

My nutrients have been too low for too long. Some corals starved to death dispite my efforts in dosing AA, coral foods, feeding very heavily, and even increasing my bioload to the point where I'm uncomfortable keeping more fish in my tank. NO3 less than 0.5 and PO4 0 for over two months. I slowly backed off off of bacteria and carbon dosing letting my LR, siporax, and sand bed do the job. Also slowly removed zeolites. I only have carbon in sump. After losing a few frags and realizing my nutrients weren't going to rise any time soon I decided to dose KNO3 to keep my corals alive. Within a few days I noticed my colors improved and my alkalinity / Calcium consumption increased. My question is will this become problematic if I still dose bacteria? Also does anyone know if xtra special contains PO4? I want to boost PO4 a little if I can.