Small pebbles will get stuck in those dagger board pockets.
I use a long BBQ spatula to knock them loose. The handle is not very long but the spatula part is really really long.
I would fabricate two new ones out of mahogany wood if the original fiberglass ones are not available. Be sure to cover the wood with tinted white fiberglass resin to blend in better.
I made a pair of rudders maybe 12 years ago and they turn out great. :
I should have made two pairs of rudders so I would have an extra set........hindsight is 20/20....
I wouldn't leave my boat in the water..........................