from 4 dht setup removed two bricks (brick[3-4]) using remove-brick and did a peer detach on those two bricks. and kill nfs-server on brick3 and brick4 manually. 

now trying to add these two bricks into cluster again.
did a peer probe - for brick3 said "already a friend" 
for "probe brick4 " said "brick4 already part of another cluster" , probe unsuccessful and failed