I can see you have been managing your humidity. I was below 20% RH and I could not get the roots to hit the edge of the pot. I was irrigating to the point of saturation every 24 hours, but they were still air pruning.
I might ditch my four inch starters, and start sowing in 6-inch net pots,,, Nah; I am too impatient to dig the root balls out, and I am too cheap to throw them away.
I do like those oversized Tea-bags that I have been seeing around.
They seem to be just the ticket, for plugging into common beds.
And compostable, I imagine, eh?