Hi. I'm new to the forums.

I was just wondering about my jade tree. First it grew some strange looking mold on the leaves. I was told it was because I was over watering it. The mold seems to be drying up now, but the tree still looks a little on the puny side. I realllly don't want the tree to die since its nearly 20 years old. Can someone give me some advice on how to perk it back up again? Is there any sort of fertilizer that I could use to make it healthy again?