201005_0509_06.jpg - wrinkled leaves

I thought I had rinsed and pre-treated the coco well enough, but a few wrinkled and discolored leaves on a few seedlings say otherwise. Pretty sure the coco is still absorbing some nutes (cations -- calcium, magnesium, potassium) from the very light feedings. They're putting out a new set of leaves every day, so it's time to up the feedings. I don't like to water young seedlings too much though -- rather encourage them to develop some roots.

Could the wrinkling be due to low humidity? That's the only thing that seems far out of the norm here -- it's been reading 15% or lower lately.