I dont see any issues with having a night light on at all, if anything it may be less stressful for them to have a night light that flicks over to full lights in the day. In my tanks its pitch black at night and when the timer kicks in all the bright lights come on and i bet its not a nice experience for them all when it comes out of the blue like that!
I've tried leaving the blue light on for a few nights now and I noticed that they are a lot more active under night light than day light
Right now in day light they are just stoning and scratching away, if not, hiding. are these behaviors normal for them?
They have also not been eating food that I put in, the last time I fed them was about 2-3 weeks ago I think