Out There in the Garden...

These leaves aren't quite to the point of needing to be plucked, but would be in a few days... (Problems are easier to see at this stage...) I'll pull maybe 4 to 6 necrotic leaves off each plant every week; not enough leaves are being affected to make me worry about the plants' overall health, but I'd like to know what's going on. This has been a continuing issue for maybe five weeks-- since about the time that flowering first began and I stopped using FoxFarm Grow Big. The pH is between 6.5 and 7, and it doesn't look like a nitrogen deficiency, but I could be wrong... that's why I'm asking. Grasshoppers were a problem earlier in the summer, and I think the bite holes are leftovers from them, but might be continuing from some other cause. Without marking the leaves that have them, it's hard to tell how recent they are... Other than the bite marks, there's no evidence I can see of any bugs/worms on the leaves, either on top, underneath, or in the dirt. I sprayed all the plants with Pyrethrin two weeks ago, but the slow leaf death continues. It used to occur only on the lower leaves, but now seems to be moving up-- these photos are of leaves taken about halfway up the plants. The strain is Critical Widow. There's a Blueberry Kush plant next to the three CW's that is not showing these problems, so I'm guessing it's a nutritional deficiency peculiar to Critical Widow. I've hesitated to add any nitrogen to the nute mix since the plants are so far into flower, but is it possible that's what they need? Is there another obvious nute deficiency that I'm missing?