m0useanswered grow question 2 years ago I don't think its much to worry about, might just be some odd gentics at play.
however it is best to rule out some other things.
Check under the leaves to confirm you don't see any mites or pests of any kind. really look and bring in a magnifying glass as these little fuckers are small.
I see on your diray there is no PH or EC levels for what your giving the plants. This also maybe a PH thing as coir needs a lower PH when growing in it with liquid nutrients. Do you have these values? or a way of testing them?
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Good Luck!