I'm no expert, but at least for Spatulata, I have experience with. Wait till the tip of the flower (red parts in the photo, and I assume that is the spatulata) turns brown. When that happens, I usually get seeds from them.
What I also do is that because the bottom flowers are the first to turn brown (they are the oldest) I actually cut off the bottom ones that have browned already and then I pinch to get the seeds, leaving the rest to continue to develop. Be careful though, because once I just plucked out the bottom bud, and I broke the whole flower stalk.
The yellow flowered one is probably D. Nagatomoi, have no experience, but maybe same thing.
Anyway, long story short, I don't think any of your flower stalks are ready yet!
TTFN
Arvin