Toof Decay - 3rd Grow

Things have been pretty smooth this week so I've been keeping to the same schedule I've been on with nutrients and watering. 1 gallon of tap water every 3 days. One feeding is 3g Mega Crop, 0.5g Sweet Candy, 1.0g Bud Explosion, 1/2 tsp Recharge, and 0.6 ml Mammoth P. The next feeding is 2-3g Mega Crop by itself. I noticed a couple of the plants have some leaves that are on the darker side and I think I might be pushing the Nitrogen a bit too much. I've been giving about half the recommended Mega Crop dose so I might do a Sledgehammer flush next watering and cut the MC back even more. One of the plants has what appears to be a Phosphorus deficiency on the lower, oldest fan leaves. I can't tell if it's actually a deficiency or if the leaves are just old. I've been adding a little P/K booster with some Mammoth P so it seems weird it would not be able to get enough P from that. The other plants are looking good so I'm not super concerned.