Can Cas13 be used with multiple crRNAs in the same reaction?
Answer is no. Because each CRIPSR-Cas(xx) system works as a ribonucleoproteic complex, so they needs to be loaded with a crRNA in order to be working. Functionality is guaranteed while each of the Cas endonuclease domain is associated with a crRNA. You maybe could use multiple Cas13 with multiple crRNA. 
In molecular diagnosis is common to use orthogonal CRISPR enzymes with different crRNA, as can be seen in this original research.