Burning Tips

Hi everyone,


I recently switched from Gavita DE fixtures to LED bar lights with LM301H Evo diodes.


I’m using the same soil, nutrients, and keeping CO₂ around 1200 ppm. However, as soon as I switch from veg to flower, my fan leaves start burning at the tips, then progressively die off, and by the end of flowering most of them are gone.


I’m measuring light with an Apogee PPFD meter, and readings are around 500–600 µmol/m²/s. The LED bars are nearly 1 meter (about 3 ft) above the canopy.


Has anyone experienced something similar? Any suggestions on what could be causing this?

Good start on information but more info would be helpful—EC, how often do you water, temperature, RH, etc.

Biggest issue is that you've gone from a grow light that generates light+a heater that warms up vegetation to a grow light that generates light and does very little in terms of increasing leaf temperature. With the drop in leaf temperature, transpiration drops and that will tend to lead to nutrient imbalances.

Also, your light levels are low. Cannabis will thrive at 800-1000µmol in ambient CO2. With the modest amount of light that you're feeding your plants, photosynthesis rates are not very hight which means that transpiration is not very high.

The plants look fairly green. I don't know that you have an N toxicity but the leaves appear to be dark green and shiny which makes me thing that you're getting close. With the change to flower, the need for N drops so a change in nutrients might help.

Off the cuff, first step would be to drop EC by a bit.

You may benefit by increasing ambient temperature, especially in light of 1200PPM CO2. Leaf temps of ~85° in veg are about as high as you want to go with cannabis with temps dropping as you enter flower, eventually going <=78° by the second week of flower.

Given that you've got all of that CO2 there, I'd look to double the PPFD. Cannabis thrives on high light with yield increasing directly with PPFD/DLI. With ~three times as much CO2 in your grow area as in the atmosphere (~430PPM), you will get a significant boost in growth and yield. Just adding CO2 is generally taken to result in a ~30% boost. If you double your PPFD as well, I would expect to about another 40-50% bump on top of that.

That's just some general ideas that could help based on the info that you've provided (light source change, photos, and CO2 levels). More specific information, as mentioned above, including photos of the plants and of the grow area will help nail down changes that more specific to your grow.

Thanks for you reply
Im using Remo Nutrients , Following they feedchart, It aways worked fine on Gavitas DE , My EC stands 2.2-2.7 at flowering, and im watering 2 times a day.
Temps are about 71.6°F on air, i will Measure the leaf temperature tomorrow with a thermal sensor. the VPD average is 1,3-1,4
RH 55%

I will try to increase room temperature without messing too much with vpd

TRY DROPPING TO ONE FEED A DAY, AND MAY BE DOPPING YOUR EC, 2,7 IS A LOT, I KNOW PPL WHO FLOWER WITH 1.3 MAX EC oops, didn't mean to shout. yes, 1.3 EC max during the whole flowering process, i don't know why ppl try to max out EC, it just seems to cause problems.
some extra heat would help as was mentioned by Delps8