I found a couple rust spots on the older leaves of the larger hubba earlier. She's not getting enough calcium. I'll get a picture tomorrow.
I found these instructions for cannabis and dolomite lime. These directions are more than I'm using, so I'll double it to 2 heaping tablespoons a gallon and mix it a few days before I need it.
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Organic Dolomite Lime - For Soil Growers
If you're looking for a way to supplement magnesium in your organic or soil setup, I highly recommend a product called "Dolomite Lime."
Note: The finer the dolomite, the more quickly it will be available to nutrients
Dolomite is a good source of calcium and magnesium and can be mixed with your soil. The great thing about dolomite is it works slowly over the course of a few months.
Dolomite has a neutral pH of about 7.0 and will help buffer pH in soil so it's easier to maintain the correct neutral pH range which is optimum for cannabis growth, especially in acidic soils.
You can buy
Dolomite Lime online, but with shipping it's almost always waaaay cheaper to pick up a bag at a home improvement or gardening store such as Lowes, Home Depot, gardening centers, etc. If possible, try to get a finer grade of dolomite compared to something that is more coarse.
How to Use Dolomite Lime for Cannabis: When growing cannabis indoors, add 6-7 teaspoons of fine dolomite lime to each gallon's worth of soil. So if you're mixing enough soil to fill a 5 gallon container, you want to add 30-35 teaspoons (about 2/3 cup) of dolomite lime to the mix. Mix the dolomite lime and the dry soil thoroughly, then lightly water it with water that has been pH'ed to 6.5. After getting the soil wet, mix the soil well and wait a day or two to let the soil settle before checking the pH and adding plants. When growing in an outdoor garden, follow the dolomite lime manufacturers instructions.
I know for certain that our ladies need more of it under the cobs then under 5 watt led's, you may have to up your mix even more under your new light. Almost every plant I've grown under them has shown some signs of deficiency until recently. I followed @BigSm0 lead and have been pouring the botanicare cal mag to them nearly every feed, 1-2 tsp gal, plants are looking better.
Roasty likey!
