3rd times not a charm. Yellowing of new growth.

[Efbespn]

Third try at this, went super conservative on this one. Yet the yellow seems to show up, no fail not sure what to do.
Here's the setup
Lights : Electric Sky es300 (300watt LED) dimmed at 30%
Medium : mix of Fox farms Ocean forest and Happy FROG and perlite.
Nute: Humboldt secret base A&B
CALMAG and Iron
Real growers recharge
Impello Tribus Microbes
Foliar sprayed with Epsom salt 1/4 per liter.
Room Temps at 82 RH at 70-80%

Need some help from the experts. Been digging through old post in all forums but can never get a definitive answer as to what is going on. I'm sure I'm not the only one who has run into this problem, I'd appreciate if someone who could share their expertise in finding a remedy. Thank you loads and good luck to you all on your grows. All the best!

 

[Efbespn]

Forgot to add
RO water supplemented with 4ml per gallon of cal mag and iron.
Ph at 6.4
Havent yet gave them nutes as the fox farm soil is still fresh from a recent transplant from solo cups to 1/2 gallon pots.

 

[m8ty]

Are you over watering? And why are you spraying with Epsom salt? It looks like nute burn on some of the leaf edges and tips.

 

[Efbespn]

Are you over watering? And why are you spraying with Epsom salt? It looks like nute burn on some of the leaf edges and tips.

Don't think I am over watering. Foliar sprayed thinking it's a mag issue.
When you ask if I over water, do you mean if I water before soil dries or when I water when soil is dry, do I flood it? I water till 20% water starts to run off.

 

[HeLLfiReZ]

Check your run off ph and tds.

 

[Efbespn]

Check your run off ph and tds.

Will have to do that when the soil dries. But will definitely check it out.

 

[Efbespn]

Symptoms seem to point to a potassium problem.