After posting, I inspected my photos more closely and noticed some tiny dots. I went and reinspected my plants with a magnifying glass. I‘ve taken a very close up photo of a bud. Aphids?

What should I use to treat this? Neem oil?

Thank you, Floral. Your advice is always so valuable.

I suggest going out after dark with a flash light to see if the flower muncher is at work.

The flower damage looks like it might be from snails or slugs, judging by the stringy excrement.

And I was also going to comment that aphid damage can create those curled leaves on new growth.

Thank you for the comments. I had been blasting the plants with the hose each day and felt like I had the aphids at bay, until I discovered a few Japanese Beetles. In addition to picking them off, I sprayed with neem oil. The leaves seem to be recovering, but the flowers continue to be munched. I’m strongly considering pulling out the dipladenia.

Did you check at night?

I did! Twice. I didn’t see anything. I’ll check again over the next few nights. Do you suspect catterpillars? If so, what is the treatment?