I kind of doubt that adding two initialised variables to your sketch will make any difference at all, assuming you fix the syntax so it compiles.
If I understood you correctly you have a program ("Vixen"?) on a PC which is sending serial data to an Arduino and you have configured Vixen to put some recogniseable strings at the start and end of each message. That would certainly make it easier for your Arduino to detect the boundaries of each message accurately. In this case your sketch would need to receive the character stream from Vixen and detect the start-of-message and end-of-message character sequences. It would use these to determine whether it was receiving a message, and whether the message was complete. Presumably you would want to buffer the content of the message until it was complete and then process it.