Please help me save this plant and finish my first ever grow

[growernotashower]

The whole plant has had it's leaf tips burnt during almost it's whole growth and a few yellow leaves but nothing too bad. Few days ago I noticed it started to get more yellow leaves and more burnt leaves tips on the top leaves as well. The only change really is I started watering it 2 times a day a week ago. I water it with 1 liter in 5 gal pot and get 20/30 % runoff. I read you can't overwater in coco/perlite, but I'm also getting a bit more runoff than 10-20%. I also upped the PH to 6-6.2 from 5.8.
To me it looks like it needs another month of flowering so I don't think the yellowing leaves are natural as well as I haven't flushed, but I am using a quarter of the feed only.

Auto flower. 81 days old. Around 50 days of flowering.
Growing in 70/30 coco/perlite with the Biobizz nutrients except for calmag by Terra Aquatica since I couldn't find the calmag from Biobizz. Following schedule at 1/4 or 2/4 dose at 6/6.2 ph at flowering, 5.8-6.0 during veg. Changed it back to 5.8 after getting an advice to lower the PH. Don't have TDS meter.

SETUP:
Spiderfarmer SP-2000 at around 6500x10 lux peak of tallest bud.
3 smaller fans
Exhaust fan with carbon filter and SpiderFarmer tent 2x4 that went with the kit.
Temperature around 73-80 during day and 67 during night. Humidity around 45-60.

 

[Zill]

Dear G,

The plants look good. Flowers are maturing. Sort of later in the grow stage, have you attempted to rinse the salt residue from the pots. I was thinking that maybe over time salts have been accumulated and now your seeing leaf burn. Bear in mind, it is probably a combination of imbalance of nutrients and natural senescent of an annual plant.

Zill.

 

[Fromunda506]

Showing signs of K deficiency. First thing that get locked out from accumulated nutes. Especially if it started after increased feeding. You can’t overwater coco, but you can overfeed it. I would heck runoff. Assuming it’s high, either flush and then reduce strength of feed or just reduce strength of the feeds and try and let it come down as the plant catches up. I would flush personally. Than can go south fast and affect your flowers both in structure and terp profile. Would not do anything too dramatic tho. They are getting there. Good luck getting her to the finish line dude. Cheers