I have a Meyer lemon in my yard and one thing I have observed personally and from researching citrus blogs is that the quality of the water makes a difference. My tree is so much happier when it gets rain water than when I water it from the tap. I am noticing the same thing with several of my other plants that are less drought tolerant than some others. It can rain for days and the plants love it but if I water them from the tap everyday the leaves turn yellow.
I think its the chemicals in the tap water. I collect rain water when I can but its never enough so I have to supplement.
