Your error has nothing to do the file writes. Your error is very common and if you had done a search of the forums before posting, yuo would have found the answer yourself.
You CANNOT have multiple tasks with the same resource. That means you can only have a single DAQmx Read for analog inputs. Get rid of all of the duplicate DAQmx Reads. You can specify multiple channels with a single DAQmx Physical Channel control and if you want each channel to have a different min/max, then use multiple DAQmx Create Channel functions and pass the same task from function to function.
