For your peace of mind and for our knowledge base, do some research.
Try unplugging it and see if it changes again. Maybe try both very short power off (like as long as it takes to unplug and plug back in) and longer off periods. If it does switch modes again, try it in other modes and see what it does.
BTW, nice tidy set up. I want so bad to switch to a rimless tank. But that's not easy with a 180g tank. I'm considering building one myself. But a replacement for my 55g with something around a 75g-90g home built will be first. I did my frag tank a year ago, but at 10" deep, it's a no brainer!