Light burn?

[SmokinAces420]

So-this is my second grow im using 2 300W LEDs to grow. Im using elite nutrients was feeding half reccomended feed in soil last week started full strangth. Im growing 4 different strains lsd, purple haze, blue dream,-and liberty haze. Lights are 22" above the plants. The lsd and purple haze are showing signs of what looks like mag deficiency at the top of the plants and showing no signs of deficiency at the bottom. The blue dream and liberty haze show no issues. I will post some-pictures does anyone have any recommendations?

 

[SmokinAces420]

 

[thesplashin]

Looks like too much light/heat. Have you got a fan blowing between top colas & light ?? Higher your light. If it was a problem with Nutes, it would begin at the bottom and work its way up the plant. When any leaf burn starts from the top, it is most likely to light/heat stress. Try to keep a balanced temp to in the room.

 

[SmokinAces420]

The plants are in a tent and the day time temp stays consistent 76F-78F. I did raise the light on that side of the tent the other side looks unaffected. The tent is in a basement with the ambient temp is 59F-62F. When the temp hits 78F in the tent vents and pulls in cool air untill the tent air is cooled to 76F. I could set the set point lower if you think that heat is the issue. The burn started to show at the end of week 4 flower and I raised the lights from 18" to 23" above the light. Two days ago I moved them to 26".

 

[SmokinAces420]

They do show some signs of potassium deficiency at the bottom but just a few leaves im just not sure if the strong light is manifesting the problem on the top as well. I increased feed strength to 100% reccomended last week (before that I was using 50%) and supplemented some tappin roots in the my water once a week. Between the 4 plants I mix up 2 gallons and put .5 gal per plant and water twice a week with 3 gal to get the 10%-25% runoff mark. So I feed friday water on sunday and tuesday. I just want to give everyone as much information as I can.

 

[SmokinAces420]

Is there anything else that im doin wrong?

 

[thesplashin]

I would put a blowing rotating fan between the Light & the plants. Even though you have a good distance between the plant and light, you can still get Light Burn. Its just like us sitting in the same spot for 12 hours when the sunshine every single day...for weeks. The ripple from the fan blowing will help stop the concentrate light being sat on one position when lit. I always sit amongst the grow for at least 30 mins, trying to get to the same height as my highest cola. If I start to feel the burn, then that the same for them.

 

[SmokinAces420]

Ok will do! Thanks for your help I will grab another fan or 2 and set them up and let you know how it goes