Those look like Superfly artifacts. Superfly (more so), Iray (less so) and other physically renderers don't like closely placed transparency planes. One solution is to add a little more "fluff" which raises lifts the close planes a little more which tends to make the artifacts going away. The other solution in Superfly is to change the renderer settings. You can also increase the max and min transparency bounces in the superfly render settings to get rid of those artifacts. It increases render times but also increases realism to have those fluff planes.