What's wrong with my Phal?

[FloridaOrchid]

My plant was very healthy and bloomed for about a month and a half but recently something strange has been happening. Usually I believe blooms wilt in the order they came in and fall off. Random blooms on my Phal have been falling off without wilting at all- they look perfect. There is no sign that its sick besides some (maybe 1/4) of the flowers have black ends on their "lips" and a couple of flowers have one dark spot- almost like a bruise. I haven't seen anything online about what this could be or if it is just normal. I attached a picture. Please help! Thank you!

[FloridaOrchid]

Some are wilting naturally and falling off, as you can see in the bottom of the photo and I'm not concerned about that... but a good handful are falling off completely open and full, so I'm curious.

[WhiteRabbit]

hmm... I do have some orchids that just drop blooms when they are finished, rather than withering first - I don't know if it's usual for a plant to do both. Any big change in temperature or humidity ?