If the plant seems like it's gone downhill all of a sudden after some weeks, I would suspect overwatering. Older flowers will sometimes get tiny black spots on the petals before dying off but usually those spots indicate a Botritis fungal infection. Combine that with the white patches on the leaves, and I would have to guess that fungus is definitely the culprit.
Be sure you're not overwatering first off, (if you are, and the medium is soggy and mushy, you'll have to repot in fresh medium), then spray the entire plant with a fungicide designed for ornamentals.
As far as the bugs go, you can wipe them away by hand, or, you might get a combination fungicide / insecticide and spray the plant with that to get everything.
Bud blast like you're describing sometimes occurs for seemingly no explicable reason (usually it happens because of a sudden change in environment but it doesn't sound like that's what's happened in your case). Everything combined the way you've described (the shriveling lower leaves, too, though that as well is normal when it happens by itself) just really sounds like rotting roots, so check that first.
Hope that helped!