hi guys
I have two dwarf trees and for some reason, they grow beautifully....BUT for every leaf that is born another one on the bottom turns yellow. what do I do?

Is it because they are dry (because of heating in the apt), lack of sun (not much I can do in Boston)...is it too cold for them next to the window?
Please help.
I dont want them to die!

Spider mites are common when indoors in dry conditions. They are found on ther under side of the leaf. If you see teeny tiny dots, and possibly small webs then thats what you have. If so just mist semi daily under the leaves, and that should knock them back, this would also help if the are too dry indoors. If it's just cold that fairly easy to tell just by putting you hand near the window and feeling for drafts, or cold. Good luck, and make sure your not over watering cause that's a problem sometimes in winter also.