Hey there! Bear with me, I'm just waking up.
Some cal mag products contain Nitrogen. You could be unwittingly adding N into flower cycle.
pH- it's a pain in the rear at times! The best thing I've found to do is save those water jugs, fill them from my tap and let them set for 24 hours minimum. I know we're in different locales with different water treatments but water is full of chems that aren't beneficial to much these days.
Lower ppm a lot. Back way way off. Lower ppm to almost nil. 200-300. You should flush with only a cal mag additive at this point imo for 1 week and reassess. You're not going to see any recovery on the current leaf damage. That won't happen but the creeping damage will stop once the errors and deficiencies are corrected.
When you flush your plant you're going to go for 50% run off, some say 100%, but really it doesn't look that bad. Normally you'd only want to water until about 20 percent comes back out, that's runoff, what comes back out when watering. Make sure your temps are good, the rh is good and don't let your pots sit in the run off. Test samples of your run off if you've received your pH meter. A cheapo meter, $10, will get you through if you store it in calibration solution properly. Keep that glass bulb clean and covered in reference solution in a little jar, not the pen cap it comes in. Use a jelly jar or something that's been properly cleaned, steamed ideally.
Let the medium dry. You can tell how dry the medium is by lifting the pot. It shouldn't weigh anything. Try not to let your leaves begin to droop though. You'll want to keep proper levels within the plant. You don't want it bone done dry and sucking everything in that gets introduced in the next watering immediately.
How many weeks in are you now?
Have you done foliar sprays or spilled water on those leaves? Do you treat for bugs? I feel like there are fungus gnats about as well.
I hope I helped some... Good luck man. I would seriously start a calmag flush.
I'm not sure where your pH should sit. Hydroponically Coco would be low, 5.5- 6.2 can be normal but you've got compost. I would take one plant and use it as a tester. Drop pH to 5.5 on it and see how it responded. That's just the things I would do and the whole ship could crash because of it. Good luck dude!
