Hi Phillipe
I would guess something small had nibbled on those leaves?
Unfortunately I am not familiar with the rate of growth on Phal bellina, but I would guess this one is not your only Phal or your only Orchid? If treated correctly, it should start showing growth soon. Perhaps you just repotted, into fairly large bark, and it needs to adjust. Roots are doing well you say, perhaps just be patient?
Anyone else please? I am definitely not the Phal expert!