How to Identify and Prevent Blossom-End Rot
At the first sign of blossom end rot, I crush one calcium based antacid tablet (such as Tums, or I use the cheaper generic brand that comes in large bottles) in just enough water to dissolve it and pour at the base of the tomato/pepper/eggplant vine. The rest of the fruit then is fine. I've used this method for years.
How often do you do this treatment. Weekly, monthly? How often do you water your plants during July and August?
For both the chickens and the planters, I crush shells a bit and then roast them slowly in the oven until browned. Crush a bit more and sprinkle in coop or potting soil I mix from a local plant nursery and a water treatment plant residue called 'sludge'...shells will keep slugs down in the planters and provides calcium to the chickens among it's other benefits.
I grind egg shells in my coffee grinder and spread them in the dirt and around the base of the tomato plants. In the dirt provides the need calcium; around the base is a deterrent to any bugs. I also give all my vegetables a good dose of used coffee grounds.
Coffee grounds contain nitrogen. Also cold black diluted coffee is good to use. I grow tropical Fiddle Leaf Fig plants and use diluted coffee on them.
I buy cheap calcium tablets from the dollar store and dissolve them in warm water to treat my tomatoes. No blossom end rot.