Three weeks ago I bought a potted key lime tree from Home Depot, that seemed healthy. A week after I had it home the leaves started to go brown. They look "scorched" What can cause this? I have watered it some, the soil is damp but not wet, I have a mini greenhouse I put it in outside. We have hard water and its quite dry in the house. Would it be helpful to filter the water I put on it? Also to mist the leaves?