yellowing,crispy,tried everything

Hello , I am really struggling to work out whats wrong. Well I kind of guessed its cal/mag or nute burn but it seems to not want to clear up or stop even after major flushing with low strenghth feed and epsom salts.

My set up is 8 plants in dr240w tent 3 lights (600s hps), airpots 15ltr cocoa,dripping low ec , run off every few days plus 2 major flushes in last week.
Nutes hesi range inc supervit ect but not using hesi pk i'm using EA boost (new product recomended by hdro shop.. 70 pound for 1 litre..I know lol)

My ec at start of 5th week flowering today is 1.3 with 3 to 4 feeds of half a litre each feed ..ph 5.8 rising to 6.1
temps are fine, good air circulation with good air intake ect.

The thing is its only 4 of my plants that are like it and i am just hoping that now at the start of week 5 flowering they will make it to the end and not need their leaves so much....at the start of week 7 i am going to stop all the feed and use gh ripen to finish them off quickly before they get really bad.. heres some pics, any thoughts or advice welcome.
The leaves started to turn light green about 10 days into flower not in any paticular pattern but mainly the fan leaves then got worse. As you can see from the pics the buds are developing just fine at 28 days from 12/12.. when I flushed with ph 5.8 and 30 litres each pot. 1 more point the problems started before the Ea boost but my concern with this product is it causes the ec to rise by alot so I am not adding as much base bloom feed as i normally would...

Did you use pre-bagged coco or brick?
Do you use drip clean?
what are the ppms of your tap?

I'm no coco expert and can't give expert advice but I can tell you where the possible F'ups are

JohnnySocko said:

Did you use pre-bagged coco or brick?
Do you use drip clean?
what are the ppms of your tap?

I'm no coco expert and can't give expert advice but I can tell you where the possible F'ups are

Click to expand...

canna pro cocoa...tap ec 0.5..using keep it clean by dutch pro (same stuff as drip clean)

To me it looks like they are being burnt up by nutrients. And from my experience nute burn leaves a mark in the overall grow.
Let them dry out well after the flush, and go back to a lite dose of base flower nutes, and drop the p-k boot.

A shot from my personal wall of shame titled Over Feeding


I transplanted 2 of these from coco to perlite and finished but I don't think it was worth the effort

Potassium deficiency going on.