started indoors need grow light bulbs. They are available in a bulb or the more useful tub. Anything other than a grow light is inadequate once the seed
embryo pushes thru the soil and the seed
Is your sunroom a all year room or more like an unheated breezeway? Are the windows Low-E or otherwise treated to repel the light spectrun from the sun that makes plants grow and carpet fade? Once you removed the plants from your light set-up what they got was not adequate. Put thin sticks in future plants and the minute the plant stem is out of line with the stick its lighting is not right.
When the fourth true leaf was out the growing
tip could have been pinched out. That makes the plant bushy rather than a tall thin skyscraper. Roots don't spend so much energy getting "supplies" up that tall stem.
You no doubt hear stories where gardeners take a outdoor plant inside for the winter and all the leaves proceed to fall off. The plant needed to be acclimated to going indoors. The reverse is true for spring seedlings
going from indoors to outside. Its a process of a week or two depending on fickle spring
That's why it's important for gardeners buying seedlings
or bedding plants to ask if the item has been hardened off. Don't assume because a plant is sitting out its been hardened off.
Don't let injured leaves remain on a plant. Clip them off as you see them. If the stem and upper leaves are healthy on the few damaged plants give the stem a support, let 4 good leaves grow, then start pinching out the top. You might end up with a standard rose
of Sharon Tree.