So I bought a hlg650r and everytime I put the plants under it they turn pale and droop. I tried hanging them 3ft above the canopy on low and everytime they droop. I then put them under my hps light and they perk back up. Nothing I try seems to work. Does anybody else have this problem? I'm thinking the red is stressing them, but then why are they recovering under hid lights.
Might be Mg. It's a common deficiency with LEDs and is necessary to form green. A subtle thinning of the leaf tips with a tendency to turn to the side is a good sign of this. Not twisting, they remain flat and healthy looking, but are not totally straight. Having the last 20mm veering off to the side just 10 degrees perhaps. Its the best sign to look for as nothing else does it.
Def think its variant dependent too. My Nice Chunk looked a bit stressed, the first cut of her performed way better. 2 Skunks looked stressed but the Skywalker was fine. Same tent, germ times and nutes.
Running 2xSP250's in a 4x4 veg. Had to lift them to 1m of the canopy, the girls love it.
IMO this is probably simple light shock. With LED's it can be difficult to judge the brightness on the canopy without a PAR meter. Most LED's provide far more blue & red wavelengths than HID. The brightness may look similar to your eyes but the plants are getting blasted.
I would allow 2-3 weeks for plants to get accustomed to the more intense LED light. Start with the light WAY far away or dim it way down. If 3 feet isn't working try 4 or 5 feet. Then increase the brightness on the canopy every few days until you're up to full power. The pro LED fixtures I was using needed the plants to start 55-60" inches away - 5 feet - but after a few weeks the tips of the plants could grow within 15 inches no problem. These were only 320 watt fixtures.
I think if your plants get stressed under leds it's because they are not getting their other demands met. High light levels require other limiting factors to be met and it isn't as easy as with lower intensity. It may be that the plant's root system is not large enough or the feed isn't optimal.