Yeah I was joking about the perlite..
Pretty sure those were ladybug eggs. It's a good lesson on why you shouldn't destroy something when you don't know what it is. Here's a link:
I've seen ladybug eggs before and they were yellow so I was thinking beetle (ladybugs are beetles but there's plenty of other kinds) or caterpillar eggs. Be sure to look at the larvae pictures I hope you haven't been smushing them. I almost did the first time I saw them but something told me to look them up before I killed them. They don't look anything like ladybugs I was surprised and happy I stayed my hand.
Outdoors ganja becomes a part of nature, part of the balance of predator and prey. I don't like treating outdoor plants with sprays and pesticides because of this. My plants have plenty of leafhoppers and grasshoppers, and sometimes I find cutworm and slug damage. But I have lots of ladybugs, predatory wasps, and spiders which balance things out. And most importantly the damage they do is minor, not to the point of a major infestation. If it's minor why fuck with it?
Of course infestations are different, be they rodent, deer, caterpillar, mites or whatever. Which comes back to the leaf spots. I'm not 100% but I don't think they're caused by a deficiency. Well, the plants could be deficient which makes them susceptible to disease. I'm thinking fungus attack or possibly bacteria. If your plants are healthy and vigorous they'll probably outgrow it. Especially since it's only attacking old growth.
I'm glad I'm not growing in a humid area I know in the East you have terrible pest infestations that require management plans. I'm still thinking potassium carbonate is your best bet. Greencure is the brand name, I mentioned it before. I know it's used by professional growers of apples, wine, tobacco, and the like.
It works by changing the PH chemistry of the leaves. Don't know if it'll work on your spots but it's cheap so it's probably worth a try. Plus it'll take out any grey mold or powdery mildew spores. I'd spray all your plants down, even the unaffected ones after a rainstorm as a preventative measure.
There's also copper and sulfur fungicides. These are harsher on the plants so I'd use them as a last resort. Not sure how safe they are to use on flowering plants. I know Green Cure is approved up to the day before harvest for organic crops.
Which comes back to calcium and magnesium which can wipe out fungal attacks by fixing nutrient deficiencies. Epsom salts is a great source as is the kelp meal recommended earlier. Epsom salts is cheap and easy to find. All it is is magnesium and calcium unlike the kelp meal which may have variable amounts. I'd probably use both, mix the kelp meal and epsom salt with water and feed them.
Since I discovered my soil is deficient in calcium and magnesium I keep finding more applications for magnesium. I find myself recommending magnesium all the time. Once you learn to spot something like that you start to notice it everywhere. And everyone focuses on N-P-K they tend to skip on micro-nutrients. Which a lot of soils are deficient in.
One thing I've learned from my experience is that plants can be deficient in Cal-Mag causing nutrient lock out without showing signs. Which can cause problems to manifest like fungal attacks.