looks as if it was slightly fogged before you used it to print -- the square corners are the tip-off. Someone accidentally leave the light-tight box a titch open? You got rug rats who have been secretly investigating things in your darkroom?

then there's the possibility that it was not completely fixed -- using fresh chemical?

Whatever, it happens. Toss it and print again.

oh yeah, and make sure your safe light is the right color for that paper AND not too close to where you are working ... safe lights can fog.