Miltoniopsis flower spike rotting and breaking

[Rross]

I bought my first miltoniopsis plant. It arrived with the beginnings of flower spikes. They grew beautifully over the past month or so. The plant looked very happy growing in my bathroom in indirect sun and good ventilation. However, on my daily check, yesterday, I was upset to see the beautiful spikes had suddenly started rotting and breaking. All I could think was a sudden cold snap - from about 25 to 15 degrees Celsius- might be responsible, or that maybe even the stake was too short. I honestly don’t know. Could anyone help me? The plant is Breathless Brilliant, and I don’t overwater it. Here is a pic.