It's really hard to tell in this photo what may be a white spot or what is from reflection of your flash.

The FIRST thing I would do is take a really soft brush and clean them off. There is so much potting medium all over them that it also makes it hard to tell.

Even though the parents aren't variegated, the offspring may be, due to genes from further back.

Or, it could be cold water spots if cold water has been allowed to get on the leaves.

So, clean them up, let them grow on a little longer, and see if variegation develops.

Barbara

Hi,
In the top photo on the topmost leaf on the right edge there is a white spot that looks to me like the start of folair mealy bugs. I agree with Barbara that the plants need to be cleaned to make the problem more visible. Please clean the dirt off the leaves and take another photo. If you find the white speck I spoke about is rather sticky its a mealie bug. Take a fine brush, dip it in alcohol and touch the whie speck. If it disolves, you have a case of mealies.
Fred in NJ

Could be water/condensation on leaves.

Doesn't appear to be mealy bugs (checked with alcohol, thanks Fred), thank gods.

I'm reluctant to clean these tiny guys, because they are literally a centimeter or two across. It's not like a tiny bit of dirt would hurt anything else other than identification, right?

RE/ dirt doesn't hurt anything:
A quick search using clean leaves + photosynthesis gave me this find:
"Cleaning plant leaves allows more sunlight to penetrate the leaves, allowing for maximum photosynthesis to occur. Clean leaves are more attractive..."
(granted they were trying to sell leaf cleaner ;)

I wouldn't be able to stand not cleaning them up a little -my first reaction when the post opened was to lean towards the screen so I could blow some of the dirt away.

I would take a soft paint brush to them or a give them a gentle bath under the kitchen hose - dry them before putting back in the window! Or even blow on them after the next watering (so you don't get a face full of dirt!)

Clean[er] can't hurt. And congrats growing from seed!!! After all that time & work growing from seed, getting to the bottom of the mystery white will be worth the effort.

North window - zone 5 might not be enough light? Maybe dirt is plugging up the works even more?