What's wrong with my orchid petals :(

[Oliviapetal]

Hi all
I'm new to this forum and found my way here because I just bought a white phalaenopsis orchid . I repotted it as the first pot had no drains and added some orchid mix from the local garden store. I just noticed today that a few of the petals are wilting or thinning away (maybe being eaten but I don't know what by?). What should I do? Thanks