Betta Fish: is he changing color? or something worse?

apologies for the bad quality photos- he moves a lot and it’s hard to get a clear picture of him haha. the first two pictures are of him currently from both sides. i’ve had him for 5 days. he was marketed as a rose petal betta. when we first got him he was an incandescent blue/purple and white. he had a few spots on his right side as pictured, but i figured it was just him gaining some color. i’m noticing the dark dots are now spreading rapidly and it’s worrying me. i’ve had all my bettas change color but never this quickly, and never from and all-white betta. thank you in advance!