Hmmmm, I don't think weather is a factor here. We've had many overcast days with cooler temps than normal but that hasn't affected the other eggplants at all. I took another look at the Mitoyos today, most are rock hard fruits no bigger than a large ping pong ball if that. Only like 3 fruits per plant. I have 6 plants of this variety in Earthboxes w/ fresh medium in full sun just like my other eggplants.
