That one in the foreground looks pregnant.
That's really great that you are feeding them. If you do decide to get them "fixed", there are live traps that you can use. I used to work at a place that was in an industrial area and the place was loaded with feral cats. My then SIL and I would trap them, one by one, and take them to a pet clinic that would deal with feral cats and knew how to handle them. We also would find the feral kittens produced by the feral cats and would take them in, tame them down and find them homes with the people who worked around that area.
I wish you luck in your endeavors with these kitties.