Windows sills are not the best place for weed plants,
as the temperature swings are to great, pots can cook,
get to extreme temperatures and cause great damage to the root zone,
at night the opposite is true, as the plants cool the rootlets shrink or retract,
irregular watering along with pools of water in the saucer easily exposes the plant to unwanted fungi issues ....avoid
Do note the red stems and at such a young age, these plants are 'cold'
the red is actually anthocyanin(food coloring) or as I say too dammm cold!!
as to the colored posts ..note the black pots are at least growing correctly
I hope you have a nice warm tent 4 them ...lol
as you have the start of a good grow
good luck!