I have a standard young pink lemon tree that is in a large 24x24" planter on my patio - it gets full sun and is usually pretty content. Over the past 3-4 weeks, there are a couple of branches that have been losing their leaves. There are about 10 lemons on the tree right now that are starting to get ripe, and even some pink flower buds...but the leaves keep falling off! :( We've had a lot of rain lately (well, a lot for southern CA), but I don't know what else it could be. Any ideas?