So let me start off by saying, I have to be one of the worst plant people. You have NO idea how many plants I have killed in the short time I have moved into my apartment. I have this one rather large philodendron plant that I have had for several months. Since my window was looking rather empty from the other plants I had killed.. I decided I would get a few more (When will I learn?

) So here is my problem:
I bought another smaller variety of philodendron. When I went to repot it.. it seemed as though the greenhouse let the cuttings grow a tiny bit of roots, and then stuck them in the dirt, because they basically fell apart and came off the dirt. I tried to fix it by sticking them back in the pot. Now it seems that the stems (where they go into the ground) is shriveling up. Also, some of the roots are exposed and kinda look moldy. I think I may overwater them, lol..
Any ideas what I can do? It was only like a 3 dollar plant but I feel bad for killing so many!!