HELP! Flowering Plants Bronze/Copper/Brown leaves!

[Hammer]

Hi I am in 5th week of flowering and my leaves on my plants are turning bronze/copper at the tips and becoming very dry. The bronze/copper is showing up on margins and between leaf veins. This is occurring on the top colas and mid area of the plants. I have trained these plants using the mainline tech. Here are some details and pics. I will upload more pics tomorrow when I have time. I really hope someone knows what is up. Thx.



Blueberry

-lower older leaves yellowing starting at the tips
-while upper leaves near the top colas are turning a bronze/copper color that starts at tips and progresses towards leaf base or show spots mostly interveinal same color.
-tips of fan leaves all over plant show slight white burntness

White widow

-this one has upper cola leaves yellowing at the tips and margins and moving towards leaf base
-leaf tips curl up brown and crispy.

Plant scenario:

-1000 w hps
-18-20 in away
-7 gal pots
​​-temp 60-77
-hum 50%
-air fan circulating
-5th wk flowering
-ph 6.4-6.5

Now heres what I've done nut wise

2 wks into flower I gave grow formula at 1.5 EC
4 wks in I have bloom formula at 1.2ec

I though I might have a cal mag issue so I hand watered the blueberrys and widow with a nut soln with cal mag added. I do not see an improvement.

Here's some pics....Any thoughts?

 

[OzBud]

The last photo looks a bit like potassium deficiency

http://www.growweedeasy.com/potassium-deficiency-cannabis

 

[Hammer]

You are probably right. After I flushed and increased nuts drilled some holes in the pots for more drainage the plants are looking much nicer now. Thx!

 

[Flockshot]

60 is pretty cold