From yesterday to today upper some leaves turned yellow

[jimmykcorn]

I'm in soil keeping PH 6.3, ppm at .5 scale 500 around, plants 18th day into flower, today is feed day so need to no what might be the issue so I can change at the feed. 4.5 to 5 day feeding schedule. just changed the plants to new Gorilla tent for the height 7'11" added another de HPS i-power 1000w was running both at 660w around 30 inches from canopy the plants were stretching pretty fast so added 2 - 32W CFL 6400K extra blue for slowing stretching. I put my hands over the plants and it doesn't seem hot just nice warm like on the beach on a holiday. Temp during 12 hours of light 69-74 degrees F seeing in Canada the fresh air takes the temp down in darkness into the 50's F.

 

[BeastLebanese]

Looks almost like light burn, how do they look now that its been a few days?

 

[BeastLebanese]

I'm guessing its most prominent where the light footprint from the bulbs overlap?

Maybe space the bulbs a bit further away from each other if you can, I'm guessing its at least an 8 foot long tent.

Hope I helped.

 

[GeneBanker]

I feel like water stands in those sections and then the light gets it. Kind of like chapped lips but on the plants leaves

 

[BeastLebanese]

I feel like water stands in those sections and then the light gets it. Kind of like chapped lips but on the plants leaves

Looks like it may be symptoms of overwatering, the way some of the leaves look like they're caving down from the sides.
Not 100% sure without more details.

Maybe someone else can chime in for a second opinion?

If they're not sleeping and you can get in a few good pics/ more details might help further diagnose the issue.