I would take the position of being cautious nonetheless. Mites, especially the false spider mites are so tiny that the naked eye can easily miss them.
But the rapid deteriorization of the buds points to an insect as the cause. Typically a mite lives about three weeks. You may not even notice them at first.
That spotted damage is so typical, trust me. Look carefully at the undersides of the leaf. Look down the length of the leaf and roll it slowly along the long axis. If mites are there the leaf takes on a "silvery cast" or sheen. I would not even attempt it without my lighted, trusty 10X magnifier. Let me know what you see.
Thrips and aphids are famous for bud kill. I assume you could see the aphids but thrips are like dark slash marks and if you hold the plant or leaves over white paper and gently tap the leaves, the little buggers should drop to the paper.
A thrip is about as fat as a human hair and fully grown is about a millimeter and a quarter long!
Good luck!!
