Thankfully, you can fix blossom end rot. While you can’t “heal” a individual vegetable that’s already damaged, you can prevent blossom end rot from happening again--on the same plant.
This lack of calcium can be caused by a few things: -There’s not enough calcium in the soil (this is rarely the case) -The calcium is there, but the soil pH is too low for the plant to be able to grab and use it