Ok here is my take.
36 hrs dark wont hurt them like that. I sat almost a week in a power outage. I could have run my generator, but decided not to. Instead I watered them when they needed, no nutes.
Now I didn't add any heat. By this i mean the room was 72 f. All started flowering which I immediately let plants have 12/12 based on when the lights in the room came on.
There is no way 1.5 days of darkness alone caused your damage. You somehow managed as well to planticide them. Maybe to much heat, and under water?, over water? over nute? Is something there you are overlooking. But certainly is not lack of light alone. Light schedules can stress a plant, but not enough to kill, unless temps or water issues are added with it in that short of time.
I might add, I maintained 72 daylight, even with plants not seeing the light, and 65 night. Just so were clear. I could have left 65 or 75 as it wasn't my first bout with losing power, wont be last.