NMoasis said: to NGA!
Your tradescantia looks like it's suffering from a watering issue, either not enough (my first impression) or too much and the soggy soil isn't draining. You should be able to tell which. Sometimes potting soil becomes hydrophobic — it gets so dry that water runs around the edges and doesn't soak the root ball.
Either ailment should be evident by the weight of the pot. What planting media are you using?
As for sun: if that window is due south, there's a chance it got overheated if it was also underwatered, but if it has always been in that location, it seems less likely
NMoasis said: You did a beautiful job! With all of that info and photos, I now think the problem is that the roots are waterlogged and starved for oxygen because there is no drainage. Repot with fresh soil. I wouldn't go into a bigger pot, especially going into winter. If there is a disproportionate amount of soil to roots, the soil stays wet too long and you risk rot again. Your peat-free soil mix sounds like it drains well. When you water, put the pot in the kitchen basin, slowly fully saturate the soil, then let it drain completely before setting it onto a saucer on your shelf. (Saucer to protect surface)
Unless Tiffany responds and says otherwise, I suggest clipping each stem by about half when you repot. Hopefully you'll see new growth soon and can clean out dead bits later. Your potting mix has nutrients in it. Start fertilizing with an all purpose liquid in about six weeks.