How often do you feed and what are you giving them in terms of plant food?
A coir grown plant should be fed several times a day.
Excess P/K yellow the top leaves. You using pk boosters at all?
seems like nitrogen excess mixed with watering or ph issue (probably ph of water using for watering issue)
Pk boosters cause more problems than anything, especially if it's timed wrong.
If your ec was 3.0 then that tells you you never needed to feed it as high as you were doing.
Obviously some stains will respond differently but generally it's overfeeding.
If your running multiple feeds a day you'd be better running at 1.2- 1.4ec, try 3 floods so you get less dryback
Pk boosters cause more problems than anything, especially if it's timed wrong.
If your ec was 3.0 then that tells you you never needed to feed it as high as you were doing.
Obviously some stains will respond differently but generally it's overfeeding.
If your running multiple feeds a day you'd be better running at 1.2- 1.4ec, try 3 floods so you get less dryback
If you are now putting in 0.7 and still getting 1.6ec out then it needs flushing and then starting with a fresh res of 1.2 and monitoringYou think i have to rise the Ec to 1,4? I thought it's better with less later this is a Autoflower at Day 76