Potted Lemon Tree Leaves Small?

I have a 2 year old Lemon tree that I bought last year in a 5 gallon pot. It had lemons on it last year and this year it is flowering, but the leaves are very much smaller than last year. I have feed it Miracle Grow and made sure it was watered plus it is summer and I put it outside to soak up the rays. Why are the leaves so small this year?

By teresa from Lynnwood, WA