Leaves dying on one plant?

I have two plants (Sour Alien and Grapefruit fly) both are getting 1/2 liter of water every 2-3 days with Humboldt nutrients 1.5 ml (per liter) Micro and 3.5 ml Bloom (per liter) with bottled water in fox farm soil. Lately the Sour Alien's leaves have started to yellow and in some cases curl and die. The other plant (grapefruit) looks great Heres some pic whats going on?
Thanks




Also pics are with the light off

Anyone? It all helps

looks like possible overwatering, i would check the roots and see if they are brown

so, imho, it looks like either a P, or K lockout, possibly both. go check out the guides for plant problems they have listed as the first four links on the plant problems forum. i'll copy and paste some quick info though. and some links for you.

Mature leaves turn yellow and then become spotted with edge areas turning dark gray.

• Potassium deficiency - add muriate of potash.

Older leaves will curl at edges, turn dark, possibly with a purple cast.

• Phosphorous deficiency - add commercial phosphate.

https://www.rollitup.org/general-marijuana-growing/1469-marijuana-plant-problems-cures.html
http://www.icmag.com/ic/showthread.php?t=11688

i would give her a quick flush (with clearex or 1/4 strength nutrient solution), and give her just straight ph-ed water for the first watering after that. see how she's doing, and then start again with 1/4 strength nutes. don't trip though, they look great other than that. no plant is going to have all perfect leaves.