Need help with an Onc. leaf issue

[smokinjoe1952]

Hi,

I have several Onc. intergenerics in my grow chamber, and and most of them are starting to get, or already have this brown leaf disease. I have researched many resources, but could not come up with a specific cause. Any identification and treatment help would be most appreciated.

Thanks,

Joe

Specifics:
Indoor grow chamber
68N-79D this time of year
Humidity 60-75%
LED lighting
active air circulation and periodic fresh air intake
K-lite 25ppm
Kelp-max
Innocucor