Wils. pbulb beginning to rot?

[Mere313]

About a week and a half ago, I purchased several bare root seedlings at my local orchid show. One was a Wils. Red Stars 'Rooster' that had three pbulbs. The roots had been wrapped in damp spagnum moss at the show and when I got it home, I potted it in some small piece bark mixture. Now the Wils. looks like it's starting to rot at the base of two of the bulbs along with some of the leaves. Is there anything I can do? Any ideas of what I did wrong? I don't see this happening with any of the other seedlings I purchased. Thank you!