Only appreciable difference I can really see is the top right has more of an elongated face/mouth. Which sex has more of a long face, hmmm, depends if trout can marry or not…
It is all about the kype. I can’t really tell on the lower left, and upper right photos. The upper left does not have a kype for sure. The lower right certainly has one. The other two are up in the air for me. If I had to guess, the two lower photos are male, and the two upper photos are female.