OP, what is your watering schedule, and do you mulch? This will probably be the larger cause of your blossom end rot. Yes, you can try and save as many untouched tomatoes immediately by adding a tomato specific fertiliser or calcium, but your real issue is probably watering.
I’m a flexitarian myself and I wish more people would just do that, just realise that they’re eating too much meat for their health anyway and cut it down to 2 or 3 times a week.