Have you tried the animate shadow clones extension? This uses a player object variable to track the clone count. When the clones hit the end object the counter is decreased. Just add the extension and the cloneCount variable to the player object.
This uses 4 objects. A platform, a player with the platform object behavior, a duck object and a duckClone object. plus, the animate shadow clones extension. (it’s an extension not an object behavior)
Edit: You don’t need to delete the clones. The extension will do that. I updated the screenshot.
Edit 2: Even though the extension deletes the clones. It looks better if they are deleted upon collision. It probably needs testing.
