will introducing 20 seconds of light during flower really mess it up?

Notice this is a old post but I had to look up if anyone has turn lights on for 30 seconds before lights turning on to water I’ve done it maybe once or twice I’m 7 weeks into flower and was hoping it won’t stress my plants

Hello, welcome to Riu @TonikOne
I wouldn't be concerned about light momentarily a couple of times but it's best just not to mess around with the dark period theres too much invested by that point.

You can get green lights/torches allegedly green light doesn't cause problems but idk how accurate that is but you could check it out if it's any interest to you.

It used to be thought that plants only reflect green light, but that's not true.

It's actually responsible for photosynthesis and plays a role in shade avoidance and probably some other stuff we don't yet understand.