Hi all, Many of our plants are exhibiting serious leaf curl, affecting young and old plants. The leaf curl does not extend to the older light leaves, or those that were healthy before the leaf curl began. Once the leaf curls, it dries from the outer edge and eventually crumbles. The lighting is 800W - 400HPS + 400MH. Water pH is tested daily and always within 6.2 - 6.9. Plants are soil based with a mix of potting soil, sphagnum moss and perlite. The potting soil is similar to Miracle Grow potting soil. Plants that get grow fertilizer, receive it only on watering days. The fertilizer is a hydroponic liquid mix that is used at its lowest if not lower mix ratio, since leaf curl problem. The young plants, such as that in the attached pic, have not been fed, even though they are now in their fifth week. As you can see, once leaf curl happens, growth is severely stunted. New leaves never get big, just curl and burn up. Bud pistols get red prematurely and resin never builds up. We have lost several plants so far. Since leaf curl has come on, all plants have been water flushed, some more than once. Cal/Mag has been added to grow and bloom fertilizer applications for one week now, in case the plants have experienced lock out, but not sure if the cal mag is working. From our research, it seems to lead to chemical burn, but we are pretty sure that the young ones were not fertilized, so how could it have affected all? The lights are on a 20 hour regimen, which has been the case during healthier crops, but thought I should mention it anyway, especially if an 18hr cycle would be better. We have checked around and can't find similiar pics or descriptions. Any help will be greatly appreciated.