Rust spots on leaves getting worse

Hey guys,

Need some help, this is my friend and I's first grow and we are running into an issue. Rust spots appeared on the leaves approx 2 weeks ago, and now seems to be getting worse rapidly in the last few days.

Unknown Strain
Growing in Coco run to waste
Using Mars Hydro LED
Currently at approx day 46, issue first appeared around start of week 6 when we added some PK13-14
Gave it a good flush around 20L of RO water pH'd to 5.8ish
Issue seemed to be under control
Started feeding again in last few days and seems to be getting worse again rapidly
Currently feeding Ozi Tonic (8mL/L) and Cal Mag (1mL/L) and RO water, pH to 5.7-5.9. ~950ppm (1.9EC)
Feeding every other day until I get 10-20% run off
Run off is around 250ppm (0.5EC) but pH is always close to 6.5-7.0 and has been all grow

I've been trying to self diagnose this all night but not sure what it could be.
Nute burn? Calcium deficiency? Phosphorous deficiency?

Here's some pics, any ideas? Thank you.

Ca def!

USE a Ca/Mg every feeding....Coco needs extra Ca!

Dr. Who said:

Ca def!

USE a Ca/Mg every feeding....Coco needs extra Ca!

Click to expand...

Thanks for the qucik reply mate, I've been using 1mL/L of cali magic every feed, as well as my normal nutes. I did just get a RO unit which may be compounding my problem. Should I double the dosage of Cal Mag? 2mL/L ?

edit: worth trying a slightly higher pH maybe up to 6.2 where I think Cal gets better uptake?

OutlawGrower said:

Thanks for the qucik reply mate, I've been using 1mL/L of cali magic every feed, as well as my normal nutes. I did just get a RO unit which may be compounding my problem. Should I double the dosage of Cal Mag? 2mL/L ?

edit: worth trying a slightly higher pH maybe up to 6.2 where I think Cal gets better uptake?

Click to expand...

OutlawGrower said:

Thanks for the qucik reply mate, I've been using 1mL/L of cali magic every feed, as well as my normal nutes. I did just get a RO unit which may be compounding my problem. Should I double the dosage of Cal Mag? 2mL/L ?

edit: worth trying a slightly higher pH maybe up to 6.2 where I think Cal gets better uptake?

Click to expand...

5ml per gallon! Your way low...

Hold off on the pH for like 5 days....If the new growth is clean and the progression stops...Your good. If it continues and gets worse..They yes, try that....BUT wait 5-7 days before screwing with the pH - it looks good.

Dr. Who said:

5ml per gallon! Your way low...

Hold off on the pH for like 5 days....If the new growth is clean and the progression stops...Your good. If it continues and gets worse..They yes, try that....BUT wait 5-7 days before screwing with the pH - it looks good.

Click to expand...

Thanks again for quick reply. 1gallon is 3.8L so 1mL/L is about 75% str I guess? I will bump it up and hopefully I can get it under control. I assume these leaves will never get back to normal but hopefully just don't get worse. Cheers

Yup, they won't "repair"....

Drop your ph to 5.5 if you're doing hydro.

Think I may have figured this out out today, got some pH calibration liquid from the hydro shop and I was about 0.3-0.4 out, reading too high. So Feeding 5.8 would have been 5.4 and I believe calcium is best absorbed at around 6.2 so could have been a severe lockout.