Yes, adding vmk0 to VDS is favorable and in actual should be moved as it gives the same policy inherited on all the ESXi host across the cluster.
However, its depends on how you have added the uplinks. Is uplink5,6 showing unused before you tried adding in vmk0. However, only 2 uplinks is quite relevant for vmk0. As a best practice, you should use your unused uplinks to other vmkernel port like vm1,2...
Please share the actual error you were facing..