Yellowing lower leaves during 12/12

So I have 5 ak 47 xtrm plants that have been in 12/12 for 35 days today ... They had some yellowing of the lowest leaves early on in flower so I hit them with an extra dose of n (advanced sensi grow a and b plus sensi cal which is 4-0-0)
Any way now they are starting to get worse and it seems as though it's WAY to much to be normal leaf yellowing in flower

However they are pretty bushey ladies and I've noticed some of the leaves in the dead middle of the plant yellow and wondering if it has something to do with those leaves not getting light???

They are grown in soil temps are low to mid high 70s rh is 40 they are in a tent in 7 gal pots

Sorry I tried uploading more and it's taking FOREVER for some reason ... Anyway I guess my question is how to add N to the equation and is it ok to do that in flowering or is this from the leaves not getting enough light bc it does seem to be affecting the side of the plant in the corner and the leaves that were behind the bush

What is the ppm and ph at when you check the runoff?

I wouldn't add N at this point.

Last time I checked it it was 6.8 and right Around 680 or so ppm

Ya I know n is bad to add this far into flowering but I'm thinking these will go around 60 some days just don't want to hurt my yield to bad

So any advise to help prevent this on my next grow?? I already feed veg nutes 2 weeks into flower (and these didn't seem to stretch at all for some reason maybe 6-8" tops)

Do the leaves always droop like that ?
Especially the bottom ones ?
If you had just posted a pic of the lower part of the plant...I would say overwatering is causing the yellowing.
You still have some dark green leaves. So you still have N to work with.

No that was right before I watered them ... I water usually about .75 liters per 7galpot when they are thirsty usually evey 2-3 days but I make sure to water till run off

A 7 gal is going to take about twice the water you are giving them. Water until you get 10-15% runoff from the bottom of the pots. If you are feeding high P bloom nutes this could be part of the cause. Container grown plants do not need the high P foods contrary to popular belief. And N is not a bad thing in flower, another myth. Plants should remain green and healthy all the way until harvest. Yellowing during flower is not a natural process of the plant. Another myth.

I meant to say 1.75-2 liters per plant sorry

And last night I actually bumped it up to 2.5 per each plant

So the yellowing is now spread to almost the top of the plants here is a pic of what I just saw at lights on

They are only at day 39 today and from what I gather they should go somewhere around 63 days

Am I completely fucked on this harvest and going to end up losing my plants days before they are ready or is there something I can do to help them?