Ok so I have Corren at the front about 20' ahead of the rest of the party, Leo is at the head of the column followed by Zinna and then Mradoric bringing up the rear. Who have the lit torches? Will Corren have one, if not how is he going to see what is in front of him? A torch lights out to about 20' radius so if Leo has the torch then Corren is right at the edge of that if he scouts ahead that far. On the other hand if Corren is the only one with a torch then the rest of the party may see what is between them and Corren but will not be able to see behind them.
This is going to be more of a classic dungeon crawl so make sure to announce when searching for secret/concealed doors and traps. If you are constantly doing so your movement rate will be greatly reduced as you have to go over everything inch by inch as you move so when entering a new space I use the characters passive perception unless specifically told that the character is searching or looking closely at something.
Since there is no immediate pursuit, I am thinking we can go slowly. Corren is going to also light a torch and search along the way. Yes it is slow, but we are already down a Carrick, and I don't want us hamstrung anymore than necessary at this point. If we hear someone/something ahead he can douse his light…