Weekend purchase diseased?

[Fredmax]

Hi, I purchased this Oncidesa Hwuluduen Chameleon from Bunnings over the weekend in their polypak section which are always fun.

I got it home to look and unboxed it and noticed the underside of the leaf has unusual markings, the plant itself is very healthy and the top of the leaves don't have marks so am happy to keep it, but more concerned of it spreading to my other plants.

Does the leaf look right or should I return it?