Burnt marks on Eva's Blue Amazon

[LinhT]

I got this Aganax Eva's Blue Amazon last Spring and kept it under the T5's all winter. As the buds were developing early this Spring they looked fine. Once they were almost ready to open, black, burnt looking marks appeared on the petals.

What gives?? Does anyone know why this happens and how to prevent it? I've seen botrytis on other orchid blooms before but doesn't look like this.