After Playing your game i realised the screen is divided in 3 parts the obstacles are a 2 block high, 1 block or middle block and stuff so whenever they are spawn make the diamond not spawn on that Y position.
Cool! I think that could fix part of the problem, I know sometimes the stars end up inside the obstacles because they are a bit faster than the obstacles, but it could be that your idea fixes it enough so it happens so rarely it doesn't matter. I'll have to implement it into the game and see how it goes. Thank you!