Hi -- I'm noticing a problem with our Sorrento lemon tree, which is 4 years old and pretty full of fruit for the first time. A few of the lemons -- still green -- are sort of drying out and getting a whitish hardness to their skin. The picture makes it look a bit like it's mildew, but it's not damp at all, it's dry and hard. The other lemons -- many have already ripened -- are great (large, delicious, meaty), but some are staying green and turning hard and slightly discolored. FYI I last fertilized with organic fert in November. We've had some miner curl, but it hasn't been too bad the past six months or so. We're in zone 10, soCal.

Anyone have any experience with this? All suggestions welcome! Many thanks.