I see that you are decimating the 1D array (which I believe is an array of 7-elements) values that acquired by the DAQmx Read function.
Since you mentioned that there are seven (7) analog inputs, are you using the physical channels as i.e. Dev1\ai0:6?
If so, you should get a returned 1D array of 7-elements (i.e. 7-channels).
You may then index each of the 7-elements out for further processes.