Some good advice about blossom end rot, I make a lot of compost so egg shells go in. I also compost using the Bob Flowerdew method. I also spritz the leaves and fruit with a calcium solution it stops the rot before it starts and promotes healthy growth.
I grow Gardener Delight cherry Toms for salad, Marmande beefsteak for cooking and salad both in grow bags in the greenhouse, and Roma plum paste toms for sauces in old urinals and in the garden.
Tips I water early in the morning, when the fruit starts to set I water once with plain water then I mix the feed and water again, the best feeding roots are just under the soil.