I've got a three year old meyer lemon house plant that has recently started to lose a lot of leaves. I moved it inside and some leaves started yellowing and falling off. I thought it wasn't getting enough light through my window so I bought a grow light and have that on during the day now. It is still dropping leaves, and they appear to be developing splotches where some of the green leaf pigment seems to be leaving areas of the plant. Eventually, the leaves start to develop yellow spots on the top and blackish spots on the bottom of the leaf. I've attached some pictures. Any ideas what's going on?
