Hmmmm, the heat might be the problem; it does get pretty toasty around here. You know, I've seen suggestions in some garden catalogs to use a sort of red ground cloth under tomato plants to encourage them to ripen (which of course they just happen to sell
) Have you tried anything like that? And a hoop house would certainly help. We had neighbors in Oregon who grew their tomatoes in a greenhouse in raised beds and that place was like a jungle!