Your pH is slightly low, but your REAL problem is that your plants are freezing cold- are they sitting on a cold cement floor? Cold soil will show MUCH MUCH worse lockout symptoms than soil at the optimal 70'F. Also, you are running MG soil.

To keep from spreading:
Stabilize temps at NO LESS than 60'F night!
Get pots up off cold surfaces
Withhold water- let the pots get rather dry between waterings, and improve pot drainage/root zone oxygenation.
FLUSH to bring pH to 6.8 with tap water. You also probably have fertilizer buildup from running a pre-ferted dirt plus liquids, so the flush will take care of both problems.

But your big issue is temperature.
stinkyattic Reviewed by stinkyattic on . Bright Yellow Patches & leaves Turning Down, & Some plants turning up! - Any Advice? Hi all, this is my first grow, sort of a fumble my way through job! my plants are into their 7th week of flowering now, we only started using nutes since week 4, but only in light amounts the plants are generally healthy but over the last few days one has had problems with the leaves turning down & bright yellow almost dayglow patches on the dark green leaves, any ideas what could be causing this? some of the other plants leaves are turning up, as in the 3rd picture, is this a symptom of Rating: 5