Manganese def? Seedling in coco

So I’ve just started my 3rd grow and already seeing a bit of an issue. Unsure what the problem is, I’m still a bit inexperienced but I thought maybe manganese?

I have one Zkittlez auto (17 days from sprout) which is yellowing between veins a bit.
Pic here:


and one GelatOG auto (15 days) in a 2x4 tent that isn’t as bad, yet anyways.
Pic here:



My light is the BudgetLED 250 watt red spec and it’s dimmed half way on a 20/4 light schedule.

My temps are around 75°F and fall to 69-70°F when lights go off. Humidity does fluctuate, high of 80% and low of 49% in the last 24 hours. I try to keep it over 60% as much as I can but it does drop when I run the exhaust fan.

My medium is Royal Gold Tupur mix which is coco based and Ive been feeding once a day using RO water only.

I started them with...
5ml/gal CalMag (Cutting Edge Solutions)
1.25ml/gal GH FloraMicro
0.6ml/gal GH FloraGro
0.6ml/gal GH FloraBloom
(pH 6.1-6.2, EC 400-500, 250-350ppm)

Last 3-4 days I’ve given...
5ml/gal CalMag (Cutting Edge Solutions)
2ml/gal GH FloraMicro
2.5ml/gal GH FloraGro
0.5ml/gal GH FloraBloom
(pH 6.1-6.2, EC 600-700, 450-550ppm)

Last night I dropped the pH to 5.8 thinking that if it was manganese it may help.

Any suggestions?

I would think Mg is your issue, not manganese. The latter would take you most likely being off on your pH, being it's not an element the plant needs piles of. Mg on the other hand, when growing in coco, is. Maybe the last pH adjustment will help, never the less I'd be sure she's getting plenty of Mg. Good luck.

CannaCountry said:

I would think Mg is your issue, not manganese. The latter would take you most likely being off on your pH, being it's not an element the plant needs piles of. Mg on the other hand, when growing in coco, is. Maybe the last pH adjustment will help, never the less I'd be sure she's getting plenty of Mg. Good luck.

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Ok I just did a foliar spray with some Epsom salt water. Will see how it goes, thank you!