New growth turning yellow

[Coco bean]

Evening folks, growing in an IWS - flood and drain, feeding Advanced nutrients A & B with B52 and Hydroguard,, 1.6 and a 6.0 ph,, under 400w bulbs on an 18/6 ,,room temp is 24/26 with 50/60 rh,,
Plants are 4 weeks from seed and being fed 3 times a day,,
All looking lovely until a couple of days ago and now new growth is yellowing and some roots are beginning to look thin and browning on the tips,,
Any help with be greatly received

 

[Coloradoclear]

What is the temperature of your reservoir? How does your reservoir look . . . Nice and clean?

 

[Coco bean]

What is the temperature of your reservoir? How does your reservoir look . . . Nice and clean?

Reservoir temp is 20 and yes it’s clean, it’s changed weekly,,

 

[Coloradoclear]

Everything sounds dialed in? Is this the first run with this strain at 1.6? Could be a little nutrient sensitive? @HydroRed, can give you an educated guess for sure.

 

[Coco bean]

They were on 2.0 but were beginning to show signs of slight nutrient burn so 7 days ago dropped to 1.8 with a drop yesterday to 1.6,,
maybe dropped too low ? Baffled why roots are looking a bit off :/

 

[HydroRed]

@Coco bean Judging by pics, it looks an awful lot like an iron deficiency. Is your pH meter calibrated and reading correctly? Micro deficiencies will show at the top of plant or on new growth. The browning on the roots looks as though it could be what is called "air pruning". Maybe try bumping up your feed/micros back up a bit for the yellowing if it isnt a pH issue, and add additional floods to your daily schedule and see if anything changes with the roots. I wouldnt recommend changing too much at once though because if something works and you changed a handfull of things at once, you wont know what it was that worked. Best of luck!

 

[Coco bean]

@Coco bean Judging by pics, it looks an awful lot like an iron deficiency. Is your pH meter calibrated and reading correctly? Micro deficiencies will show at the top of plant or on new growth. The browning on the roots looks as though it could be what is called "air pruning". Maybe try bumping up your feed/micros back up a bit for the yellowing if it isnt a pH issue, and add additional floods to your daily schedule and see if anything changes with the roots. I wouldnt recommend changing too much at once though because if something works and you changed a handfull of things at once, you wont know what it was that worked. Best of luck!

Yes meter is all calibrated and reading correct, I am going to change the reservoir today and will put nuits back up to 2.0,,
I was a bit weary of adding another flood ( they were having 3) incase the root problem may of been caused my too much water :/

 

[HydroRed]

Hard to overflood with hydroton. What are your flood intervals?

 

[Coco bean]

Hard to overflood with hydroton. What are your flood intervals?

First is 1 hr after lights on,, then 6 hrs and 6 again,,