I have two nursery-grown lemon trees planted in an open, sunny area SW of the house in central Texas. Each produced over 100 lemons the first year, fewer the second, and have set virtually none the third. We keep them bushed for ease of maintenance, and covered, with heat lamps, during freezing weather. We have had a lot of rain and numerous overcast days this year, but few the last couple of years. One tree puts on rapid new growth, while five feet away the other is much slower. Our soil is rich, dark, deep, and well-drained. Any suggestions would be helpful. These are very lush plants, so should we prune? And if so, when?
I have listed a couple of links to help you.
I do think weather conditions may be your most likely issue, but familiarize yourself again with the watering and fertilizing requirements.
Also the pruning instructions in the article below.
With a little tlc I think you can get your lemon trees producing again.