Leaf problems

Novice grower here. I am now in my 6th week of flowering and I noticed a few weeks ago that the tips of my fan leaves were starting to curl up and were brittle to the touch. I suspected it was a cal mag defiency, because I am using a coco coir/perlite mix and forgot to mix in cal/mag, so for the past week I've fed it a plain water cal mag mix. I've ruled out light burn because about 60% of leaves have been effected not just ones near the light. I suspect it is nutrient burn.

info: week 6 of flowering
feeding schedule: general hydroponics 3-2-1 bloom, past week plain water with calmag
avg lights on temp/hum: between 85-90 degrees farenheit, 35%-40% avg humidity
strain: chronic hash
medium: coco coir perlite

90 degrees I'd say that's a touch to high should be 70/80. How many plants and what lights you using? And back of the nutes

I can't really do much for the temps. It rarely hits 90. I could vent cool air in, but I have a eagle eye neighbor who notices everything. Even noticed and commented on the fact that I had one window open in the middle of winter. I have 9 plants. The lights are 600w HPS. what do you mean by back of the nutes?

Don't use as much nutes. How many lights u running?

What's the pH going in and going out? I have found that almost all nutrient deficiencies are caused by pH being off.

you cant just stop feeding them for a week growing in coco, if your giving them MG give them 30% of your normal feed aswell and bump your ph up to around 6.3

my soil ph is between 7 and 7.5. calmag water is about 7. and nute water is 6.00. i have a single 600w light

if my ph levels are off, how come the grow is so robust? it looks like i'll be able to pull 2-3 zips off each plant.

you said you are growing in coco not soil, you should be PH ing at 5.8-6.3

I am growing in coco coir, my mistake. then I guess my ph meter is either broken or inaccurate. it did measure 6.5 after i poured in calmag water the other day.

the tip burn is from overfeeding, and thats probably causing some kind of lockout. the only thing i've seen burn edges like that is potassium def., but the damage from that is usually a dark copper color....try to stay around 6.1 in coco, i know everyone says 5.8 but i was getting a lot of problems with cal. and mag. at 5.8, when i started centering around 6.1 problems went away

Roger A. Shrubber said:

....try to stay around 6.1 in coco, i know everyone says 5.8 but i was getting a lot of problems with cal. and mag. at 5.8, when i started centering around 6.1 problems went away

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I agree. I try to stay around 6.0 going in and out. I too was experiencing cal/mag problems at 5.8, fed it twice daily at 6.3 and within a day or so my runoff was around 6.0, and the problems stopped.

ok, thanks a lot for the help.