Help! Lower leaves on plant showing dark brown spo...

Looks like a cal mag issue. I don't get it because you are using a cal mag additive and the GHE formula does contain some cal mag too so you should have plenty of it available. You nutrient dosage looks a bit soft , maybe you should increase the dosage and take a look at the water runoff to search for an eventual ph fluctuation.

hey there, sorry to say , but this is actually pH fluctuations , this you can see from how the burn is splotchy like that. You need to slowly normalise the pH by cutting out anything that raises the pH like kelp extracts , and lower it every so often until you hit something like 5.8 . hope this helps !

Hi HiyaMaya You plant looks good don't think you should worry to much. Your plant has symptoms off calcium deficiency you all ready taken necessary measures by feeding full strength Cal-Mag straight away this should stop symptoms spreading. I will recommend you to use 1/4 recommended dose call mag or 0.5ml per litre. Every feed With other nutritions you feeding the plant. Until about 1 week before flushing your plant. Remove those Sick leaves they only taking power of your young plant growing those leaves won't help much with growth any more because they been sick and not working at full potential And as the die you could end up with dead leaves or leave Mather in your soil not recommended. Personally I try always to remove sick leaves. When situation is under control. (Only a suggestion could those spots on those lower leaves be from feeding Nutritions ended up Like drops on your leaves and so burned them?) Hope this helps. And good luck with your grow.

Although it could be cal mag, Are you sure there's no little critters under those bottom leaves as one of them looks nibbled....?

Jinks is right, only I wouldn't let them be cannibalized, reason being is the nutes they recover doesn't out weigh the chance of pathogens and pests.. a leaf in a weakness state is a vector for said issues.. your call but I'd remove them..

You got it. Calcium deficiency. If you fed full strength Cal/Mag you'll notice these symptoms halt but the affected leaves will not come back. I usually keep those damaged leaves to be cannibalized and remove them once there's nothing left to take. Good call👍 and good course of action you've taken. All will be well and they ARE looking great. Cheers and happy grows😉✊

I'm not a professional but yes it looks calcium to me too. your coco doesn't contain these two in it so you should add it to your regular feeding.