Strip all but two or three top leaves. Remember a cutting does not have the roots needed to support the many leaves that are present on a typical cutting. No need to feed because the cutting doesn't have roots.
Putting a cutting in soil (soil-less mix), from the start, is best. If they are started in water they will develop "water roots" and that won't help with the growth. Overwatering will kill them.
Colors probably won't be as vibrant as they were outside but by mid-February the growth will be increasing and gradually they'll be lovely. Do not plant them outdoors until all chance of frost is over. Planting at the same time as you'd plant tomatoes - late May in the northeast - is safest.
As Scarlet mentioned, don't allow leaves to touch window panes.
