ats and tampa bay saltwater live rock "the package"

Ok currently I have a 75g with maybe about 50 pounds of live work and i set my ats up about 3 weeks ago. Algae is starting to slightly grow now and ha in my tank is slowly melting away. I am planning on doing a rebuild using Tampa bay salt water "the package" live rock. Sould I let my ats mature a bit more before I do my rebuild or can i go ahead and start on it. Tbs live rock will contain 150 pounds of live rock which is waaay more than I currently have in my tank. The package comes in two parts 75 pounds of lr them after initial cycle the otuer half come a bit later. So will my ats currently be able to handle the cycle or will it hurt bacteria growth in my system for bioload. Kinda need a safe procedure so I dont do something horribly wrong.

Also I just tested my nitrates after a week and a half of no testing and they went from 2ppm to 20 ppm. But ha is receding in dt. What should I do. Cut back on feeding? Or let ats handle it.

Should be fine... let the scrubber run.