I've seen this happen before with them, slight warping that requires them to be turned. I run slotted on one of my vehicles, and though they tend to stay cooler than regular rotors (which is the whole point), once they do get baking hot then can warp sometimes easier than regular rotors due to less surface area holding them together.

The only solution to prevent it that I know of, and it's worked for me on the 2nd set, is getting the rotors cryo dipped (liquid nitrogen, then warming, then dipping, then warming again). The cycle hardens the metal without making it brittle. Some rotors you can get treated from the factory for a little extra, and some areas there are local shops who can do it.

The thing about turning them... not every shop can do it so call them and ask them if they have experience turning slotted rotors. Shops who don't know how to do it might chip the edges of the slots.