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- fine-ass '22 harvest!
mate, the key is that in-going ppm vs. out-going,.. you have too much nute salt buildup in there, and it's starting to lockout one or more of the micronutes, others as well likely... many of these micro's are immobile within the plant, so they will show on tops first and worst,... Also some general nute burn happening too, from the tip and margin burn,... i see some K toxicity starting 9margin ?teeth? tips browning out),........ lights at the top might be too close too, may not burn per se, but can overload the photosynthetic machinery and cause problems, or magnify existing ones,... I do see some up-curling along margins too, a sign of overly intense light... those HLG units are superb, and bloody powerful!
... So, pH is an issue likely with nute build-up, but in this case, I'm going to recommend a proper flushing, so it's sorta moot if you do this.. Until the ion load in the soil is reduced, nothing good is gonna happen!... put through usually 2-3x the pot volume, with preferably RO/Di water, or low pp as you can get,... those self-fill machines make nice water for much cheaper if they are around where you live, or a water store,.... do it quickly, to limit the time the roots are waterlogged to prevent suffocation and damage them,... 20min window there abouts,... test the run-off after first gal for pH and ppm's to make progress,... get that run-off down to 400ppm,... On the last pour, it's wise to restore nute balance again with 1/4 strength nutes, to make sure a bit of everything is available,.. you can add a dose of that nice Microblast (love that stuff!) in as well, go 1/2 strength on that....
You can speed drainage some by placing a couple paper towels on top of a small stack of newspaper, and placing the pot on it.. this will start a wicking action that will draw off excess water faster-
- roots will thank you for it,.... If you have a root tonic and inoculants, add those in that last pour through with the nutes,...Then, we wait and see,....
... meantime, like Mog said, look into getting a soil pH probe, like the Accurate 8 (love mine) or a tricker, more $$ electrode type unit like Blue Labs has,.. this is basically a modified pH meter, which is for liquids only,.... Used right, the A8 is plenty good for monitoring your in-pot pH... 
>>> some things to contemplate, more in the Defc. Pic Depot, in the colored section above this one,....
