Roma tomatoes with black edges/spots

https://imgur.com/a/ugKoxTM

I started these guys from seed and probably about 1 or 1.5 months ago they started getting some black/purple around the edges. Didn't seem to be harming them, so I was lazy and let it continue, but now it's getting pretty bad. As you can see in the one picture, it doesn't seem to affect the bottom of the leaves.

The tomatoes have been growing okay. Some blossom end rots, but I've gotten plenty of good fruit off of it in the last week or two.

I fertilize them once a week with that nature's care fertilizer. They're in 5 gallon containers with a wicking reservoir in the bottom (has drainage) that I fill every day along with soaking the soil lately to combat the 90+ degree heat. Full sun. Zone 6a.