Checking your plants once in a while when the lights are off will not/should not cause any probs.
I can't tell you how mayt times I have checked my plants with a reg. old flashlight with zero ill effects. Just don't get in the habit of doing it everyday. Light leaks, where there is a constant small bit of light entering your room for hours on end is where you run into probs.
I grew outdoors for years and there was lights on outside all the time-the plants always had some form of light on them, and nothing happened to them. No herms, etc...
But better safe then sorry.
growbe Reviewed by growbe on . Visiting the girls during the dark period For some reason, I had to check the plants during the "night" (5th week in flowering) I've read once in one of the threads that green light does not disturb the plants in the darkness, so I used a flashlight with a green filter. Is that correct ? Rating: 5