twotrees hydro grow #1

Hey guys and gals, on week 4 of this indoor, hydro grow and I just hit this plant 5 days ago with fox farms sledgehammer for its first flush. Before this, the plant was growing very well, but a few days after the flush I started noticing spotting on the leaves that appeared glossy and bronze, and the new growth on top has started to yellow in the center of the leaves. Is this a result of the sledgehammer flush? I don't think it's root rot because my other plant got the same treatment, roots look the same, and its thriving very well, very green. My next feeding is in two days. Should I flush this plants roots in tap water before changing the reservoir? What do yall think? This is my first grow, hoping to start flower in two weeks as I don't have much room for light ;P thanks!