There was a plant in the office that was growing ok but it hardly had any soil in the pot and all the roots were exposed so I bought a bag of soil and filled up the pot, then I watered it. Since then the plant leaves are completely droopy and some of the leaves are turning yellow. I feel the soil and it always feels moist. I have stopped watering it so it will dry up but it doesn't do anything. How can I save the plant?
Yellow leaves are a sure sign of overwatering or poor lighting conditions, so at this point there's really nothing that can be done except to repot the plant into fresh (dry) soil and not water it as much. It might help to plant it in a pot with some drainage holes in it (and then put a saucer or plate or some type of dish underneath it) or line the bottom with loose stones. Once it stabilizes you should see it perk back up again and you can water it minimally going forward. Depending on the type of plant it is, it may only need water once a week or even less.