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.