7 week's into flowering problem ?

Hi there, I'm 7 weeks into flowering and I've just noticed yellow curled up leaves on my 4 plants.
I'm growing in a DWC system called nutriculre bubblebox,600w light in a growtent. My humidity is between 50-62% , water high 60'sc and air temp 58 - 72 c.
I change my water and nutes fortnightly and this lot of water has been in there for a week already.
Yesterday eve I had no problems but this eve this appeared on all the plants.
Ps ...the plants very in height but the closest is 14" from light with a fan just below the light. Even the smallest plant is affected with yellow leaves so am I correct in ruling heat burn from light out ??
I'm really worried as I'm only a week out from flushing !!

didnt see you mention your PH? Need some more info. Looks like a PH or too much nutrients imo, could be a lot of things really. They kinda are looking pretty done too, you checking trichs?

It's my first grow and have had no help other than online. I've always made sure my ph is between 5.5-6.1 and it's 5.8 today.

Just checking diary and I'm only 4 day's off 8 weeks into flowering.
I'd say roughly 80% of the hairs have gone from white to bent over brown (forgive any wrong terms).
I was going to flush on 8 week but would you all recommend doing it asap ?

The yellowing is only on the biggest fan leaves and near the top of plant.

fullonpower said:

Ps ...the plants very in height but the closest is 14" from light with a fan just below the light. Even the smallest plant is affected with yellow leaves so am I correct in ruling heat burn from light out ??
I'm really worried as I'm only a week out from flushing !!
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note this is taking place on the higher part of the plant and the leaves might be starting to curl up on the 1st and 2nd pic

http://www.growweedeasy.com/heat-light-stress

I am no expert on plants but I do know a few things on weather tools. I would double check the thermometer make sure nothing is messing up it's reading, if your using a dry and wet mercury thermometer lightly tap the glass on the dry one, and come back in a few min to reread the thermometer.

On a ship there are usually 2 sets of thermometers on each wing of the bridge, some officer on watch intentionally leave one side open so it can be effected by the ray of the sun so they would know if it's a good day to do outdoor activity or avoid the sun, a shaded thermometer will tell you the air temperature which is more accurate for weather, but one exposed to light will give you the air temperature and the heat from the light and that is what your plant may be experiencing, heat build up.

burnt . leafs turning twisting . sure sigh . its telling you the light needs to be pulled away, its rejecting the light by twisting leafs. keep in mind the leafs are like solar panels they will move towards the light . if there is to much light or heat from lamps it will twist up like it is now. to close then burn plants. and plant goes into survival mode smaller buds. yes smaller buds rom a to close of a light ! to far away. then the plants stretch . small buds. just right place ment plats stands straight up . taking making those big buds. placement is key in lighting. you always have to adjust them , learn how to read the plants. as soon as you see any twisted leafs then raise the light 6 inches try that . and so on . you can cut those leafs off or pull off before those brown leafs start to get into the bud. wont hurt any thing just makes it look ugly killing the value.

But if it was light burn surley the closest leaves to the light would be affected. And the smallest plant is farther away from the light but some leaves are still affected so I've ruled out light burn.

This is light bleaching from an old plant i grew in 2008, had a 400w 3 inches from the tops.

I would check on heat stress, leaf curling upwards on the sides seems to be only cased by heat stress as far as I checked online. creating a gentle breeze with a fan should do the trick.

I would get a 100X magnifier and check those trichs cause they look about done from this angle. If thats indeed the case get flushing and dont worry a bit about your fan leaves. They are history anyway.

Rl420 & nfl I think I'll take your advice and after a few hrs of research finding similar advice I'm going to flush tomorrow. Cheers guys

Good luck man, feel free to post some pics of your glorious harvest in a week or 2

Cheers ...will do.