Thanks for that rockwool link, Weedhound, very informative. I also think the rockwool retaining so much water led to the problem. It was suggested to me that the over-watering has led to root drowning, which is causing a nutrient deficiency, and that I should apply a foliage feed of sea teas and half strength fish fertilizer... not something I would want to do if I'm experiencing over-fertilization. So, I'm still confused.

I'm using the same 600w HPS for veg. The thermometer has a long sensor wire, which I have dangling so that it reads from the plant tops. The plants are about 3 feet below the light, good ventilation.

Given the temperatures and distance to the light, I highly doubt that the issue here is temperature-related. But I'm not sure what exactly is going on, so I'm still confused as to how to fix things.
Baruce Reviewed by Baruce on . some leaves thin, curled-upward, browning edges Hello all, I'm a newbie, on my first grow. I just switched from 24-on to 12/12 yesterday (600w HPS) , and today when the lights came on I noticed that about half my plants have varying degrees of a leaf issue that I'm unsure about. Some of the leaves have begun to curl upwards along the edges, with accompanying browning and a thin appearance. There's also a bit of yellowing on all of the plants, which I was told was signs of growth and not to worry. But this is new, and I'm concerned and Rating: 5