Dont know..

Everytime this problem pops up it's always biobizz nutes. Fact

Just guessing here, but im leaning towards a ph shift. Did you ph the mix after cal mag was added? And whole plant looks a bit light to me. You missing some nitrogen somewhere? I have a plant that looks similar to this currently. I took some earthworm castings and added like a 1/2 inch layer of it on the top. Then ph'd water for a couple times of watering. Mines greening back up nicely, but found my ph pen was also wrong messing with me. Once sorted all seems well again. Im using different nutes though. Mine are dry time released and I didn't use enough or its used up by fast growing plant. Just something to think about. Typically from my experience, those types of spots are calcium related from a ph shift. You got a back up pen to test with? Best of Luck! Happy Growing!

On one hand, they are experiencing light stress, give them a longer dark phase to recover. Everything else is just speculation, you should make a diary so we can better see what you've done. Lower the pH to 6.2, skip the nutrients, just use tap or osmosis water, they probably have a blockage due to an imbalance in the substrate.

Damaged leaves won't come back. If it continues, I would check runoff and soil pH levels. Might be something wrong at the soil level. Also looks to be showing phosphorus issues possibly

Looks like too many ppm’s of Cal Mag were added at once. Like if you followed the manufacturer instructions on the bottle without knowing how many ppm’s it could represent. Adding any nutrients must be done using an EC/TDS meter

cal mag is fertilizer.. you should add it all together when you fertilize. mix in the product containinng calcium last. Remember, despite the name, calcium and magnesium are 2 unique elements of nutrition. they are mutually exclusive things... 2 unique cations with different sets of symptoms when levels are not sufficient. is this only the top leaves? I think it's intensity of light.

I had similar problems with BioBizz; too many salts accumulated afterward, preventing the plant from properly absorbing nutrients. I flush it with pH 6.2 Water And the EC values measured were far too high in the water used for treatment. After the treatment, they received a light dose of fertilizer again and were in excellent condition. What is the pH and The EC value of what is rinsed out of the plants?

I had similar spots and in my case it was caused by burn after I watered my plants over the leaves. So it was a sun burn from water droplets. The damage of such can show more than a week after it was caused, which makes it harder to pinpoint. Of course do the usual checks like checking the underside of leaves for pests and observe if it spreads (if it was caused by water droplets, it can look like spread because of the delayed appearance so don’t confuse those)