Answer: Avocado leaves can curl when the tree is overwatered; the stems will become soft, as well. I suspect both your trees are showing symptoms of too much water, or soil that doesn't drain well and remains soggy for long periods of time. Try adjusting your watering schedule, or making a watering well or watering basin beneath each tree. Do this by mounding up a few inches of soil in a circle around the trunk of the tree, about 12" from the trunk. Use this basin to water your tree by filling it with water, allowing it to drain, then filling it a second time. Once each week should be as often as required by your trees during the growing season (less in the wintertime). Watering in this was concentrates the moisture over the root system and allows it to trickle down, wetting the entire root mass.
Best wishes with your landscape!
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