Question about stealth. I have these two Dero hiding in this cave to ambush the party. The top Dero rolls well and is unnoticed. The bottom Dero doesn't roll as well and is instead undetected. The top Dero goes first and fires off a bolt. Then one of the heroes goes and moves up to hit the top one and he's carrying a torch. Do they automatically see the bottom Dero now that there is no cover blocking them?