If you take your fish from darkness to light, they will always dart away frightened and hide and get a bit dark showing stress. They are basically being blinded by the light and need time to accustom to it. Because discus are known to be tank darters when startled by sudden light, I have my lights on a timer and time to come on after the daylight lightens the room and they start moving around in the tank....so...during the summer season here that equates to 8:00 AM for my tank. My suggestion for you would be to do the same thing, invest in a timer. They are inexpensive. Discus have been known to knock themselves dead by darting across the tank out of fright and banging into the other side. When I have young discus that need to be fed before I leave for work in the morning, I get around the darkness/light issue by installing a dimmer switch on my dining room light where the tanks are. I slowly, over a period of maybe half an hour, bring the light in the room up from very dim to normal, they have adjusted from dark to some room light by this time and I can safely turn on the tank lights without them fleeing in fright. Hope this helps.