Mimosa Cake Auto

Yes! Definitely overwatered. I would try to take it out of there and place it in to a sock. With a knife cut through soil arround the seedling.. maybe 3cm to each side and pick it out and place it in to a sock. Sock is like a fabric pot.. it absorbes humidity from the soil and let's root breath. You also can put a small fan blowing at the sock it will dry quiker... transplant back to soil when leaves rise. Water your plants only when soil drys out completely.. you'll know it by the weight of the pot.. bad water practice can lead to many things like fungus gnats or root rot. Good luck

Looks like overwintering. At this stage you should be able to just wait it out. If you really want to do something you could turn over the soil by the edges as it dries to get more wet soil to the top and dry out. Also add some holes in the side of the bucket to help get oxygen into the root zone. Remember the more you mess with things the more stressed she will get. You would be surprised how much of the time the best thing to do is nothing.