In my experience, mg def usually shows as tiny golden spots between the vein structres on a leaf. You can fix this with epsom salts, not too much, maybe 1/8 to 1/4 teaspoon in dwc. Or just use a fert that has enough mg in it. I'm guessing since you're using GH that you're using the micro nutes stuff too, which probably means you've got enough mg in there. Plus from your description, I don't think it's mg deficiency. Also, doesn't your fert have calcium? Read the contents to see what's there. In my opinion, Dynagrow 7-9-5 is a great fert for DWC. It has all the micronutes you need. So now what? Usually brown spotting can mean ozone damage or heat damage and since your day temps are 80's I'm wondering if it's related to heat. There's a good chance that it's getting hotter inside a grow space than just 80 degrees. If you think heat could be a problem, consider putting in another fan or a larger one, or try to run the light during cooler parts of the day/night. If you've given that much superthrive, I don't think I would give any more unless you change the water. You don't need much of that stuff. You have to decided if the fert you're using is adequate. I haven't read the contents of GH in a long time as I don't use it, but I don't remember it having everything, like boron and sulphur and such. You want a fert for DWC that has everything plants need and is easy to use. Dynagrow is a one-bottle fert that can solve alot of nutrient problems. Just follow the instructions on the back - it's one teapsoon per gallon of water in hydro. Less for a soil grow. It's unlikely molasses will help, but you can try it. I think it's more for soil grows, but then I've never used it in hydro. I don't think it will hurt if you wanted to try it.
polishpollack Reviewed by polishpollack on . Brown/tan blotches on leaves ----------------------------------------------------------------------------------- What is your experience level? (first timer, novice, experienced...) 4th grow, 1st time hydro (5 gal bubble bucket/dwc) Your Equipment: .1) Type and wattage of lights. (MH, HPS, CFL's, tube fluorescents, LED's) 150w HPS .2) Distance from tops? 8" .3) Reflector type? (cool tube set-up, bat wing, enclosed reflector, bare bulb...) Rating: 5