Master Gardener: What to do about itty bitty oranges

Q: My Valencia orange tree, 40-plus years old, has always put on a good crop of large fruit and last year, with all the rain, it produced extraordinarily large oranges. This year’s crop produced a good yield, but the fruit are much smaller. Do you have any idea why they are so much smaller this year?  They are still sweet and juicy.
A: If your tree still looks healthy and is producing fruit, it may just need some fertilizer. I recommend using granular fertilizer especially formulated