You don't have clowns - you have het clowns. A het clown does not look like a visual clown, but is carrying the clown gene. You have 100% het clowns because one of their parents were a visual clown (the other was not).
You are correct in that breeding a visual clown to a visual clown produces all visual clowns. The pairing I listed above is for pairing two het clowns together, which is why the odds of producing a visual clown are lower.