Stunted seedling?

Nothing wrong with that.Iv used domes on my seedlings for decades.I only use them for a matter of days though..I never grow without root boosters which really help witht he health of the plant.The best being house and garden roots excellerator.As soon as she shows those first true leaves she wants a little nutrition so now she wants it now.I give mine a third of a dose from around day 7 to 14 then half dose for a week then full dose by day 20 depending on how they're doing.

1 - remove the humidity dome........seedlings do not need high humidity, only clones do. Seedlings need good air exchange to function properly and air movement to strengthen the stem. Humidity domes encourage diseases and suffocate plants. 2 - you need to feed your plant, coco coir has zero nutrients and compost has almost zero macro nutrients. Your plant is starving and this is why the growth has stalled. Your diary indicates no feeding as yet, you basically need to feed from day one when growing in coco.