A friend got me a lemon tree seedling which I planted in good soil and have kept in doors since receiving it (I got it in November and I'm in Michigan). It's starting to look very bad. The leaves (there are only 5) are starting to curl under and get holes in them, and the perimeter of the leaves are turning yellow slightly. I have some fertilizer, 15-30-15, which I diluted in water appropriately and fed to it about a month and a half ago. Does anyone have any idea as to what could be going on with this little guy?