Brown spots on some leaves

Recently on some leaves brown spots have started coming.
What are these and how do I sort it?
Thanks

THEY LOOK A TAD YELLOWISH/LIGHT GREEN, YOU COULD SPRAY THEM WIH SOME WATERED DOWN SEAWEED SOLUTION.oops caps lock. its on the older leaves, see of it spreads after the seaweed solution. then ask again, but the newer leaves look ok, so just see how it go's.

Hgrow4 said:

Recently on some leaves brown spots have started coming.
What are these and how do I sort it?
Thanks

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Phosphorus deficiency

I'd say cal/mag deficiency. How much phosphorus do seedlings need? May need some nitrogen, but not much. Alfalfa meal top dressing and worm tea should fix the problem.

warble said:

I'd say cal/mag deficiency. How much phosphorus do seedlings need? May need some nitrogen, but not much. Alfalfa meal top dressing and worm tea should fix the problem.

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Wrong. Calcium deficiency shows on newest growth. And phosphorus is one of the 3 main nutrients needed from the start. Nothing says magnesium deficiency at all. But whatever.

That's coco and perlite correct?

What are you feeding and at what strength.

You can't treat coco like soil.