In my experience leaves will curl in the heat. Maybe they need a little water. Every other week is nowhere near enough food. I feed my containers with every watering, with a water soluble fertilizer at 1/4 strength, which is almost every day. If your container mix drains well, which is the key, there is almost no chance you can overwater during the summer when plants are in maximum growth phase.

I have this issue and I've read it can be caused by several things but is often not an issue in the ultimate health of the plant. I've also read that it is most common in determinate and early varieties. I have a Kimberly that has terribly curled leaves just like in your photo, but is otherwise healthy and putting on tomatoes like crazy. None ripe yet but nearly every blossom has set, which is not the case for my other uncurled plants. I am trying not to worry about it, but it does look bad.

That planting media looks dry to me. Put some mulch
on it to help retain moisture.

I used to container my tomatoes until I got a garden.

I had to water daily to keep the moisture level up. If
the containers drain well, it's almost impossible to overwater.