I can't see too clearly from the photos, but not seeing anything to worry about.
Lightly open the flower where you think the rot might be and see if you can see any signs of mold inside.
Budrot almost always starts inside your flower and the earlier you catch it the better.
If you do see mold, you need to cut the top of that flower off and make sure to remove all the rot.
Do not spray with anything, just keep your humidity on the low side and make sure you have good circulation.