I'm going to start scaling back the timing on my Martian night, converting to SID 15 mins per night, every night until my plants are clearly flowering again, then I'll slowly head back the other direction to see how far I can push back and keep them flowering. That should eventually tell me where the threshold is, and by extension, the time factor of the light spectrum I'm running.

The first night is tonight!

The current schedule is:
10 hours daylight
5 hours Martian night
8 hours SID
1 hour Martian night

which tonight is changing to:
10 hours daylight
4 hours, 45 minutes Martian night
8 hours, 15 minutes SID
1 hour Martian night

so you can see the pattern. I'll keep the daylight time and the 1 hour daybreak the same throughout.