Welcome to Orchid Board.
I'm not a Cym expert but my first Cym did the same thing and there was nothing wrong with it, it's just the move from one enviroment to another that caused it.
The temperatures you quote are actually quite warm for Cyms in the winter. I do have one in the same temps(ish) at the momment so I can enjoy it's blooms inside. However many of them actually like cool temps in the winter and my other one is in the 40-50 range in my greenhouse.
It's possible the nursary you bought it from kept it cooler and the change in temp to our house has caused this. It's actually a common problem with several types of orchids, that the change in conditions (not the conditions themselves but the change) can cause the flowers to 'blast'.
Your humidity seems pretty low, but I don't know what these like. I know Canada can be a lot drier than here in the UK, I start to think it's getting low if it gets down to 45%/50%. However, as I said, I don't know what these really like.
I'm not sure if the roots should be checked on this, as root rot can be another cause of flowers droping early. If it were a Phal I would advise sliding it out the pot and taking a look, but I'm usure if that's a good thing to do on Cyms or not as some orchids get upset easily by disturbing the roots at the wrong time of year.
Sorry I can't help more. I'm still learning about Cyms myself. Hopefully one of our experts will be along soon. I've actually edited your thread title as I think putting Cym in the title will help get the right people looking at it.
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