Is this some sort of disease?

[JambaJungle]

Actually, there are only two petals. The other three are sepals. The petals and lip develop inside of the 3 sepals. This difference accounts for why the petals morph but not the sepals. The fact the sepals and petals share similar color and markings is to be expected, especially in a phal.
It is difficult to see the base of the petals in the photo due to how the flower is so tightly cupped. It appears they may actually be notched, similar to the lip. If so, it is a very strong peloric effect.