Background: I grow in inert soil (with some gypsum added for cal/mag), and a few weeks ago I came to the realization that I was definitely causing nutrient burn, as I wasn't properly flushing the plant with each water. I noticed this because leaf tips began to crisp and curl up, and many leaves were dark green (you can see some crisped lower leaves in the pic). Since then, I flushed the soil and haven't even fed nutrients at all (assuming the plants store the excess and use it for weeks to come). However, I flipped into flower recently and I noticed some of the new growth started getting this dark color on the leaves, and some of them are still curling up a bit as well. pH is good, temp is good, humidity is good, etc. This is my first grow, so any help would be appreciated. I started to think that it might just be the normal color of the strain (Jack Herer) but I couldn't find comparable images on Google.