Actually, more than hard. A few tomatoes have rotted on the vine . . . completely. Never had that happen before.
First . . . suggested remedies.
You can buy commercial sprays, such as Green Light's Blossom End Rot Spray, Bonide Rot Stop, and Ferti-lome Yield Booster. You might also visit your local drug store and buy epsom salt and apply it as a side dressing. Epsom salt is the treatment recommended by our local radio organic gardening guru.
Once it shows up I don't believe there's anything to be done about it. I just toss the tomatoes, but that's because I have so many plants I'm pretty much guaranteed to get all the good maters we can eat and more than enough to share with neighbors. If I didn't have so many plants I'd let the BER afflicted maters ripen, pick em, cut off the end, and enjoy! BER does not diminish the taste. Just looks bad.
My experience with BER pretty much is like what Carolyn Male, a retired professor of microbiology, describes in Blossom End Rot (BER) in Tomatoes
Both my father-in-law and daughter-in-law this season have grown BER-free tomatoes. They got their plants from seedlings I grew! We have similar soil, spaced them about the same, and gave them about the same amount of water at about the same time of day. Into each planting hole I included worm castings, manure/compost, and a time release fertilizer with calcium. Every few weeks I fed them Medina Hasta Gro Plant. So why was I cursed and they were blessed? Who knows?
Two seasons ago my father-in-law was the one cursing his luck with BER while I was BER-free. Last season we were both a little bothered with it.
I can tell you that my plants do provide lots of blemish free tomatoes, after tossing the BER afflicted fruit. My biggest headache now is staying ahead of the birds and squirrels! :-)
Carolyn still posts frequently at Tomatoville, although it seems to off-line for some reason at the moment...I have NEVER seen that happen. I'm sure there a number of informative threads there concerning blossom-end rot. I have dug up so many great ideas re: growing tomatoes at that site it is nigh impossible to employ them all. 150 varieties here in Red Hampshire; all plugging along...that doesn't count all the volunteers coming up in my raised beds...so many that I have just blown off using them for any other veggies...I want to see what comes up.