New Brassavola nodosa is dropping leafs.

[Wade Coleman]

I recently purchased a Brassavola nodosa "minnie mouse" about a week ago and over this time it has dropped about 5 of its leaves; most of which were newer, younger leaves. They shrivel up and turn purple from the bottom up and you can easily pull them out. The roots that were growing are now slowing and the tip has stopped growing on many. I am hoping that this is just a temporary adjustment to its new environment, but I'm not sure. It is sitting in a south facing window growing in a large rock medium that retains virtually no water, so I water about once every 2-3 days. Does this sound like a normal thing that new Brassavola nodosa's go through? I've never had one before, so I'm not really sure what to expect.