Brown streaks on new cattleya

[chulaorchids]

I think during it's trip from the grower to you it was probably a bit mishandled, like mashed in with a bunch of other plants and the leaves on the new growth were bent, that will leave a brown streak where the bend was.
The next leaf will not show that damage. Your idea of bagging with a bit of sphagnum is a good idea and will enhance the root growth that is missing. (That is a gorgeous Catt)