Eggplants are like your tomatoes and peppers - the more sun and heat the better. I don't think 5 hours of sun is enough for eggplant. Mine get 10-12 hours and produce only reasonably well. I think mine need a little more attention to fertilizing and side dressing during the growing season. Also, variety is something to consider. Dusky do well for me but I haven't had much luck with Japanese varieties. I'd suggest trying a few different varieties next year to determine which will do best in your situation.