We are having trouble with our eggplant. They seem to get a hard skin on the bottom of the eggplant that starts from when the fruit is still small. As the eggplant grows they split, even though they are only about the size of a tennis ball or smaller. Help? What is causing this? Is it a disease? Or maybe the growing conditions? We live in a sub-tropical region of Australia. Lately the weather has been quite humid with heavy storms... wondering if over watering could be a problem???