Sliders and painteds require huge tanks with ample filtration, heated water, basking area with UV light, and a varied diet to avoid shell problems, RI, pneumonia (biggest killer of them) etc etc.. I've owned them before and it was a big hassle..

As for releasing them, in my opinion, I don't see why people would have a problem with it since they are native. Some people do but it doesn't make sense. If they are healthy, have clear eyes, no signs of infection, etc, then there is nothing they could give to the wild turtles.

Considering they actually lived this long in a terrible environment then I suspect they are both wild caught and have great immune systems. A captive hatched turtle likely would not have lived so long without the proper set up. Especially the heat and UV.