I need help please with my chinese elm bonsai tree. I bought it in July and it flourished in the conservatory. When the weather started getting colder, I watered it less and moved it from the conservatory (which was like an ice box) to the kitchen window (slightly less cold, but still not warm). Was this a bad move? Recently all the leaves have been dropping off quite rapidly (is this normal in winter?) and I've noticed that the soil is a bit white and mouldy looking. What have I done wrong? I hope I haven't killed it. Is there anything I can do?
P.S Forgot to say I live in the not so sunny UK!