[Z]

Nick, Johnny, Morgan, Lewis, Melanie, Michael, Nina, Sarah, Sky
Shore, Strauss, Drake, Woodhouse, Green, Crane, Marshall, Prince, Whitehall

Bit of detective work... If we are to assume that N, M and S are all contained in the killer's name, then the following combinations of names work:

Nick Marshall
Johnny Marshall
Morgan Shore
Morgan Strauss
Morgan Woodhouse
Morgan Marshall
Melanie Shore
Melanie Strauss
Melanie Woodhouse
Melanie Marshall
Nina Marshall


Therefore definitely innocent: Lewis, Michael, Sarah, Sky - because in none of the surnames do the letters M/N or N/S appear together, meaning the killer's surname either has a single M, N, S or the combination of M/S... so Drake and Whitehall are innocent.


^^Updated version of my previous post

Edit: The confirmed names list:

Braden = Nick
GypsyGoth = Johnny
LemonJam = Morgan

happyland = 1 isolation
MTVN = 1 isolation
Zee = 1 isolation

Jordan = 0 isolations
Niall = 0 isolations
ukturtle = 0 isolations