I bought this house back in 1997 and it came along with this lemon/lime tree. In the first few years, it gave me about 10 limes per year. After that, I didn't see any more limes. It does have a lot of flowers every spring, but they fell off by the end of summer. I tried fertilizing with chicken manure and azalea food in late winter or so, but never succeeded. What can I do? Please advise.