Problems after moving to LED

I recently switched to a Growers Choice ROI 680W LED from 600W HPS. I had started some seedings under a t5, then put them under the LED at week 2. It immediately kicked their ass, mainly droopy leaves and just stunted growth. I have been fighting this plant for 3 months now, and while she is passed the light fatigue, I am fighting something else. I grow in pro mix, 5G pots, well water, feed mega crop and add calmag. I started feeding 3g/gallon megacrop and 3ml cal mag, and have slowly ramped both up to 6g megacrop/gal and 8ml calmag. I am noticing leave tips and edges still purpling, both old growth and new. It doesn’t seem to be as bad as it once was, but is still happening even with elevated feeding. Any ideas?

I also started an auto in the tent the same time
I brought the seedlings under the light, and it did ok and is just now finishing. I have started to notice it’s leaves are getting a few brown spots as well, so here is a pic of her for reference. It’s gotten worse with her the last few weeks, and I have been feeding much less as she is super close to being done

What kind of temps and humidity are you averaging?

Temp 78-80f, humidity 45-50 during lights on and 60-65 during lights off

How close is your light?

Something in the well water? 8ml g calmag is too much, theirs ca and mg in mega crop already.

RobinT said:

I recently switched to a Growers Choice ROI 680W LED from 600W HPS. I had started some seedings under a t5, then put them under the LED at week 2. It immediately kicked their ass, mainly droopy leaves and just stunted growth. I have been fighting this plant for 3 months now, and while she is passed the light fatigue, I am fighting something else. I grow in pro mix, 5G pots, well water, feed mega crop and add calmag. I started feeding 3g/gallon megacrop and 3ml cal mag, and have slowly ramped both up to 6g megacrop/gal and 8ml calmag. I am noticing leave tips and edges still purpling, both old growth and new. It doesn’t seem to be as bad as it once was, but is still happening even with elevated feeding. Any ideas?

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How close is your light? I grow with LED's and have had similar issues. My main issue was the LED being to intense (to close to plant or turned up too high) .. to me its looks like LED light burn. LED light burn shows itself as symptoms of nutrient deficiencies, it is totally different from HPS light burn. Took me several grows to figure this out. Raise your light or dim ot down and I bet they will improve

The light is 19” above canopy right now, it has been as much as 26” away. The light is on 80% right now and has been since the the 2nd week they were under it. Last night I ph’d my root zone and it was 7.0, way too high for pro mix so I am attacking that first. I have considered this plant doesn’t like the light, but am going to reach for lower hanging fruit first. The auto that I cut down last night was significantly further from the light, and it started showing similar signs about 5 weeks into flower. I did start cutting her feed back and was also grown in promos so the light burn theory doesn’t really hold on that plant but I am not ruling it out.
I will follow up on what the more intense ph regiment does for her.

Excess Ca will block Mg and P.Looking at your plants I would say your low on Mg and P.I maybe wrong but promix has lime in it,megacrop has ca mg and your adding 8ml calmag.
Try remove the calmag or lower it to 1 ml per g.
Or none at all,feed to runoff to remove the build up.
Just my thoughts.

Mag sulphate for mag but I'd go with some seaweed solution either by folder feeding or direct into soil if it's real soil

Seaweed will have everything you need and more. But check the mag cal content.it may be different where u liver to where I live

The issues are much older than the calmag usage. Some guys have claimed that big LED's require more calmag, and more macro nutrients as well due to increased VPD, so I raised humidity and tried throwing much more calmag in the first attempt to figure out this new environment. I agree it looks like its lacking phosphorus, and having a ph of 7 makes some sense in why its still growing. My plan now is to drop the calmag back to 1.5 ml/g, megacrop 4g/g, and drop the ph of the solution to 4.5 or so and feed. Will update

dopeedogg said:

How close is your light? I grow with LED's and have had similar issues. My main issue was the LED being to intense (to close to plant or turned up too high) .. to me its looks like LED light burn. LED light burn shows itself as symptoms of nutrient deficiencies, it is totally different from HPS light burn. Took me several grows to figure this out. Raise your light or dim ot down and I bet they will improve

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How far do you keep your led's now, and how far were they before? I have kept mine at 80% and 22-25" the entire time on this girl.

RobinT said:

The issues are much older than the calmag usage. Some guys have claimed that big LED's require more calmag, and more macro nutrients as well due to increased VPD, so I raised humidity and tried throwing much more calmag in the first attempt to figure out this new environment. I agree it looks like its lacking phosphorus, and having a ph of 7 makes some sense in why its still growing. My plan now is to drop the calmag back to 1.5 ml/g, megacrop 4g/g, and drop the ph of the solution to 4.5 or so and feed. Will update

Click to expand...

Just change one thing and see,then the next.Will help for future grows.

I burned my clones with LED, had to wait a few weeks for new growth before they bounced back.

RobinT said:

having a ph of 7 makes some sense in why its still growing.

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How so?
Why in the world would you drop ph to 4.5?

Maybe double check.. I see ph in the low 6's being used for most pro mix grows.

Agreed. Excessive cal and or mg. Lots of CA and MG still in the media. I would cut all extra calmag. Feed consistent ec and ph.

What calmag are you using?