So I bought a Lingonberry plant from Amazon and I've had the plant for about 5 days now. When I first got it, it had a few leaves that were completely black. I pulled them off thinking that maybe they were just dried out dead leaves. But now that I've observed the plant for a few days, I've noticed that some of the leaves develop a tiny black spot and then turn almost completely pitch black overnight.

I cut off a couple of stems to propagate and even the leaves on those are developing black spots one by one.

Any idea what it could be? I included some photos.