Where are the last four secret castle stars?

Did you try the black hole on the wall? (it's in the room with the JOLLY ROGER BAY portrait)
Or the red bricks at the courtyard corner. (there's a hole under them)
The other white hole opposite of the RAINBOW RIDE portal
And the Black bricks on the moat (you have to break them with Wario(there's also a hole under it))
Tell me if you got these four already
And I'll get you some more

There is one that I can only think of right now. It is the other one in Peach's slide. You have to beat it in less than 20 seconds. Hope this helps!

There is one behind the waterfall outside the castle. You'll need Wario's brutal strength to get past it. In there you need to collect 8 red coins. 6 red coins are near each other. The other two are close to each other.There is another one below the moat. Drain the moat by ground-stomping/pounding the two pillars in the basement. Then go out of the basement with the door that is revealed. Go to the left when exiting, then ground-stomp/pound the big block with Wario(again). Slide down the ramp and get the Mario cap. Go back up the ramp to get the red coins you might have missed. Go back down the ramp and go along the path to find the last ones. I'm not sure how to get out of there. In the room with the Jolly Roger Bay painting in it, search high to find a square hole. Either use Yoshi's flutter kick or backflip into the hole. Use the coins in there to breathe underwater. Collect the 8 red coins and the star will appear at the bottom middle over the black star thing. In the place where you can change your character, jump into the right side stained glass window to reach the secret slide again. Repeat it, but make it in under 21 seconds, not 20. Take a shortcut by jumping off the ramp to the ramp below you. To do that, I think you need to jump off on the left to reach the ramp. Just keep going normally after that to make it in under 21 seconds. There is two more at the Boo Courtyard. One is where you'll need to attack alll of the boos by ground-stomping/pounding all of them except for Big Boo. A star will appear somewhere in the courtyard. Next, go to the red blocks and punch each one to clear a path to a hole in the ground. Jump into it. Collect all of the 5 silver stars in the Battle Fort to get a star in the Star Sphere. One or two are in the red brick blocks, one or two is held captive by Goombas, and the last one is up the pole.

Hey brod101 I do have those stars, but thanks anyway.