3rd week of flowering, mid-top fading

[geralds]

Hi guys I’ve posted about this last time and can’t seem to figure out what is causing this. I have some Trilogy OG under 3 1000 de lamps, and some under a HLG 550 led. It seems to happen every time I hit this point in flower at three weeks just as I defoliate. So I pick all the yellowing leaves off and kinda forget about and it turns out decent. But I’d like to figure this out maybe with you guys help. The lights are kinda close just like every other time about 18”. The plants are in 5 gal and get fed like 4 times a day when the lights are on. I’m feeding a modified Lucas formula of 4micro 10 bloom in flower. I have temps and humidity under control. I do drop the micro from 6 to 4 at flip just wondering if this looks like they need more nitrogen. I also started GH Floralicious at .5 and Kool bloom at 1ml. Total feed is about 650-750 runoff is close to that. I use calmag maybe once a week if I remember. Could the lights cause stress like this even if my temps are in line? It actually seems like the plants under the led have it worse but it could be just the different spectrum playing tricks on me. Anyway I also have c02 at 1000ppm. I know that’s a lot of random info but hopefully you guys can’t help be nail this. Thanks

 

[Anthem]

Looks like you have more than one deficiency going on. If in fact the problem is worse under the LED I believe the problem is Calcium and Magnesium (Cal Mag) but you may have to supplement with additional Magnesium. I would start adding 6 mls per gallon of cal mag. In a perfect world I would use no "N" cal mag. Mendocino has a no "N" cal mag. If you still are seeing Magnesium deficiencies I would add epson salt to the mix at 1/4 teaspoon per gallon.
Secondly, it looks like you are experience some NPK lockout. I believe that if you clear up the Calcium and Magnesium issues the plants will start to uptake more NPK and the problem will resolve itself.
LED's coupled with high CO2 levels will eat large amounts of Calcium and Magnesium in Coco and Hydro.

 

[geralds]

Ok yeah that makes sense for sure. I always do this in early flower. They look great at week one so I stop giving cal mag. Guess thats probably my first mistake. Thanks I’ll give it a try