One node to three node cluster performance difference

I’ve been working on trying to put together a POC in work for using Couchbase as the storage for a service in work. I currently have three instances of Couchbase running on 3 vm’s with boot2docker. With current configuration file on a single node, using wrk benchmarking tool it can get 2245.01 req/sec, however when I add two more nodes the req/sec drops down as low as 50req/sec. I have been changing configurations and searching them internet to no avail for the last while. Would anyone know any reasons as to why the drop in performance when the nodes increase?