If they still drag when you’re not pulling the lever……
The pistons do have a tendency to stick a little. Take out the pads and then pull a rag soaked in white spirit through the pistons to give them a good clean. Then pump the lever a little to bring out the pistons a bit (don’t over do it or you’ll get air in the line or pop a piston) and use a small flat screw driver to apply a silicone lube round the exposed edge. If you lube them a few times after each ride they shouldn’t stick anymore. Do the white spirit thing again when you next change the pads.
Then again you might have a slight warp in your rotar.