I was given an easter lily today, and it's beautiful! It's the first time I've ever had one to add to my indoor plant collection. There's just one problem - it looks like the soil has been soaked, and there are mites and fungus gnats in the soil. What kind of soil mix should I use to replace the dark, thick, rich stuff that it has right now, and what's the best way to get rid of the gnats and mites? I would really like to keep this gorgeous plant, so I'd like to take care of the problem as soon as possible.