Early signs of light stress/burn?

[Dutch_cultivator717]

Hey guys, so I’m having a little bit of an issue. It looks like on the top parts of my plants there are early signs of light burn or light stress. Not 100% sure this is what is happening only because my wife or 26 inches from the canopy in about 30 to 40% light capacity. My luxe Reading about 12,500 Luxe. Temperatures have been steady in the daytime 75 to 78 and 968 to 70°. I did have minor nitrogen toxicity two weeks back but that was fixed with a quick flush and ppm’s back down to 1000. Is this just minor nutrient burn? The lights are also on 1212. Anyone have any suggestions

 

[hotrodharley]

Tell us more about your wife. How she fits in.

 

[Dutch_cultivator717]

Tell us more about your wife. How she fits in.

My bad gotta love voice to text! My but my light is 26 inches away*

 

[hotrodharley]

My bad gotta love voice to text! My but my light is 26 inches away*

Use an infrared thermometer to determine temperatures at the canopy. They’ll bleach from light too intense. They’ll burn from high temperatures and especially in low humidity situations.

 

[Dutch_cultivator717]

I have two ac infinity probes at each side of rent at canopy level and I get those temperatures I listed. My humidity has been about 40-50% and no higher or lower. I’ve read people using a luxe reading of 30,000 and not having any issues so I figured 12,500 is perfect. Also two fans blowing 24/7 but not directly hitting any sites.

 

[Lockedin]

I have two ac infinity probes at each side of rent at canopy level and I get those temperatures I listed. My humidity has been about 40-50% and no higher or lower. I’ve read people using a luxe reading of 30,000 and not having any issues so I figured 12,500 is perfect. Also two fans blowing 24/7 but not directly hitting any sites.

Hi Dutch,

Nice grow! I'm still very new, on my 5th grow; but I might have a couple things for you:

Probe location - the side of the tent will not be accurate. re: more air moving along the flat walls & less radiation hitting the probe will skew the readings.
--- Hang one probe center and a few inches above the canopy - there's the hottest reading.
--- Hang the other probe center at soil level - highest rh is here.
--- I move a temp / rh meter around the tent often to tune airflow (still building out my 4x8 as I go...)
- sides of the tent, - finding dead air spots where budrot could happen
- in front of intakes (3x 6" passive ducts pulling from the outside)- I pull from outside, so I like to see what temp / rh is coming in
- on top of LED light case - surprisingly cool.
- next to the AC Infinity probe - calibration they're within a degree / % of each other.

Based on that, I run my canopy temps (lights on) from 78f - to 83f (occasional swings outside of range)
RH has been tougher for me to get a handle on, my region can have huge swings in a 24 hour period.
So far, I had budrot on my second grow, but adding clip fans cured that.

 

[ComfortCreator]

12.5k lux is good for about the first several days from sprout. I cant tell how big they are but that light reading is way low.

 

[Dutch_cultivator717]

They are 11 days into flower. I was at 15,000 but then tips started turning. Thought maybe it was light burn

 

[Dutch_cultivator717]

Hi Dutch,

Nice grow! I'm still very new, on my 5th grow; but I might have a couple things for you:

Probe location - the side of the tent will not be accurate. re: more air moving along the flat walls & less radiation hitting the probe will skew the readings.
--- Hang one probe center and a few inches above the canopy - there's the hottest reading.
--- Hang the other probe center at soil level - highest rh is here.
--- I move a temp / rh meter around the tent often to tune airflow (still building out my 4x8 as I go...)
- sides of the tent, - finding dead air spots where budrot could happen
- in front of intakes (3x 6" passive ducts pulling from the outside)- I pull from outside, so I like to see what temp / rh is coming in
- on top of LED light case - surprisingly cool.
- next to the AC Infinity probe - calibration they're within a degree / % of each other.

Based on that, I run my canopy temps (lights on) from 78f - to 83f (occasional swings outside of range)
RH has been tougher for me to get a handle on, my region can have huge swings in a 24 hour period.
So far, I had budrot on my second grow, but adding clip fans cured that.

Okay gotcha, I’ll have to move them to new spots when lights turn back on! This is my third grow but being extra cautious cause first two grow didn’t go to well because of not having the right equipment

 

[ComfortCreator]

They are 11 days into flower. I was at 15,000 but then tips started turning. Thought maybe it was light burn

I have relatively small plants going this time and they are on a 20/4 cycle and they are getting 40 to 50k lux for those 20 hours. My guess is your gauge is wrong AND you have too little light. New growth will be paler at first until it builds chlorophyll into the leaves. Not enough light is often the limiting factor, in your case you are gun shy on the lighting. If you give them too much you will know. Go up 2 to 3k a day or every few days.