Blossom end rot

Blossom end rot

We kind of came late to the tomato game this year, but bought a patio type plant and two roma plants for our balcony. After initially being worried they wouldn't pollonate, I discovered there were tomatoes growing. Then a few days ago I found the largest one on the patio had what I assume is blossom end rot. And now I see the 3 smallish roma ones growing do too. They were planted in new potting soil, and are outside so have been getting regular rain and watered when we've had a dry spell. I read somewhere it can be a calcium deficiency, is that correct? Best way to correct it for future fruit or is it too late now?
Kitchen decor: should be fixed now :)

Kitchen decor: should be fixed now :)

Shady spot,  hostas, want some opinions

Shady spot, hostas, want some opinions

Pretties

Pretties

new room, so much space!

new room, so much space!

Tomato Help!!

Tomato Help!!

The cactus that would (NOT) be dinner..and peas!

The cactus that would (NOT) be dinner..and peas!