Considering you have a melanurus and a sixline, you really can’t have many wrasses at all.
I would ditch the Melanurus and sixline. Then I’d get a couple of other peaceful wrasses. I assume you like the sixline due to its pattern?
Why not hunt yourself one of these brutes?
Trade in the sixline and get the smaller 10x more peaceful
Pseudocheilinops ataenia. That is assuming you have a low activity tank currently, these guys do terribly with aggression and need to be added into a lower stocking tank to then establish into a higher stocking tank.
Then to replace the melanurus, get yourself a smaller more peaceful
Halichoeres. I know that these can outcompete mandarins however, generally these guys don’t peck the rocks nearly as much. I would personally get a
Halichoeres leucoxanthus, this was my female (I know it’s not the best photo).
And then for some more up in the water column activity, get yourself a Cirrhilabrus species. I personally love Cirrhilabrus lubbocki - I have both variants of this species and they have gotten along for the previous two years

You can see 4 from my wrasse gang in my 4’ tank in this photo and the two lubbocki’s are that ‘line’ of purple. The indo variant is on the left and the Cebu is on the right.