What could this be? I can't figure out if it's a lack of nutrients or a pest?

calvin.m16

Well-Known Member
Calcium deficiency will usually cause rusty patches on leaves, this looks like early stage magnesium deficiency. You could add pure unscented epsom salts (magnesium sulfate) @ 1 teaspoon/gal in your feed water. Use more or less depending on how plants respond. Give the plants a few days after application and they should look better. If you can't get or don't have epsom salts you can always use more calmag! :bigjoint: :lol:
 
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