Day 40 of flower and just 1 plant is starting to show some odd yellowing on newer leaves near most bud sites. All other leaves are happy and healthy.
Light is led drawing 475 watts from the wall at 18" from canopy. Daytime yemp are 82 at most with 50% humidity. Slight upward cup on leaves so I was thinking light burn or heat stress???
I think heat stress, I see some leaves cupped, they act like that to retain humidity, try to rise the light if possible. Are they LED? Looks like those brownish spots could be Calcium deficiency, can you post a pic of the whole plant? 
When I get home I’ll take another pic and yes I can raise the light.
Here is another pic I took this morning
I was also thinking heat stress / light burn. I do feed 1.5 ml of calmag every feeding. I do use RO water but I added a calcite filter to my RO for calcium and to raise the ph.
dont know about nute burn, but i see your temp and humidity is not adjusted for proper VPD for flower, according to calculations made by Northern Loki (dont want to spam with mentions) on this thread:
for humidity of 50% you need temps from 70 to 77 F, if she is really trying to retain humidity (if she is loosing it too much), then that might be your solution, but then again, it should show on other ones also, so i would check about nutes, maybe post pics of other ones also so pros here can inspect…
I was wrong, as it appears in the new growth looks like some immobile nutrient deficiency, perhaps Manganese?
Pleas do look in the back of your leaves if you see anything weird (white spots, brown poo, eggs …), everytime I see white spots I get nervous because I cannot distinguish if a plant is just frosty or it has spider mites like this one … 
when i zoomed in on end of leaf:
from what i just saw here:
this looks like mites problem… do you have a magnifier or something to get a better look?
I examined the leaves with a 30x microscope and saw nothing.
I’m not sure mites would just attack upper/ new growth and leave everything else alone would it?
Yea, i tought about this on my ride to work, neither would leaves go yellow on edges… Hmmm ive been looking around, ive foubd this pic:
And i think i see manganese defficiency here in late phase, and also your other plant in 2. pic on upper right side seems like she has manganese def in middle progression by this pic… Thats all i can say, i dont want to spam with unnecessary info anymore, i hope youll find solution!
Thanks, I appreciate the help. Think I’ll raise my light a few inches and feed some calmag next feeding. I ALWAYS PH my water to 6.5
To me I kind of looks like a combination of calcium and manganese. I have 4 plants going right now but only 1 looks this way.
Recommend calmag dose is something like 3ml per gal I’ve been giving them 1.5 ml per gal along with my other nutrients.
CalMag has Magnesium, not Manganesium, I don’t think it is a Calcium deficiency (moblle nutrient) as you can see it in the younger leaves, glad there’s no mites …
Any suggestions @George
I certainly didnt see and bug after closely looking at about 6 different leaves.
Hi there my friend
Razing the light and add a fan for circulation
Try epson salts 1 tablespoon per gallon on the next watering looks like mineral deficiency magnesium?
Or like @George said
You can mix some epson salts with water and spray plant before lights on Should see some improvements quickly when leaf feeding
Paps
Should I water with just epson salts or can I also add my other nutrients?
From reading looks like maganese effects new growth like mine and magnesium effects old growth. This issue is only on upper new growth near buds
I just remembered, there is also this:
Where its shown that excess calcium can demand more manganese intake, if your base nutes get nitrogen from calcium nitrate and you give cal mag also, it could be that, combined with your plant being special princess that wants more attention than others, your calcium ammount is just lil bit too high, i think epsom salts are solid advice, along with some manganese (dunno how you would get that)… Let us know what worked for you!
After doing some research and looking at more and more pics at looks like possible broad mites. When I get home I’ll do a really close inspection.
Watch this it will help allot.
All the years I have grown and never once had and kind of bugs. If I have mites I’m going to be freaking pissed
Hope not 
, they like high temperatures and low humidity, that’s what you’ve got. Spraying Epsom salt diluted in water when lights off looks like a good advice. Take a damaged leave and inspect the back with a microscope or magnifying lens, hope you’re safe …
O sorry to hear 
Hey, what color are they, can you describe them pls? Could they fly?
And yeah that sucks dude! Bugs just wiped mine out.
