Phosphorus deficiency or nutrient burn?

Hello again Rollitup members! NEED your help again with identifying some issues I'm having with my plant here growing in soil.

Looking at the pictures below, does this look like some kind of deficiency or is it the result of too much salt buildup? I was doing a water-feed-water cycle and have just gave it its first flush with PH'd water. I am suspecting Phosphorus deficiency because of cold temps...I did notice blackening leaves early on...is this a latter stage of P deficiency? Any help would be appreciated. Thanks in advance everyone!

Bump!

Looks like you have both, overnuted and a start of Cal / mag deficiency.
Really dark leaves ( in most strains ) is a sign of too much N.
Too cold of an environment usually shows up as redding of stems and stalks. A P deficiency can cause this as well.
I would just start flushing it with 1/4 strength ( or less ) nutes for a few watering s and wait to see how the new growth comes out.
Like next time you water..give it clean water so it comes out the bottom and then give it 1/4 strength nutes.
You want to get the salt build up out but not deprive the plant totally of nutes.

Also what are your temps and RH ?

It looks pretty burnt to me.