I've been using "Tomato Maker" (4-2-6) fertilizer, which supposedly has enough calcium to prevent blossom end rot, but I'm still getting blossom end rot on my super marzano tomatoes (no BER problems on any other varieties I'm growing this year).

Are there other things that can cause blossom end rot besides calcium deficiency? Is the super marzano variety (or plum tomatoes in general) particularly susceptible? Could my plants still be suffering from calcium deficiency even with the Tomato Maker fertilizer?

In case it would be helpful to know, I live in the California Central Valley, which has hot, dry summers, but spring this year was unusually cool and rainy.

I'd be interested in any advice on what, if anything, I can do now to reduce blossom end rot on this year's crop and also what I can do in the future to prevent BER from turning up at all.