Honestly looks to me like all are definately male

. I am basing this on odontodal growth, thickness of the pectoral fin, and most importantly head/body shape. They all have male heads, the only one that looks the least masculine is #3, but I suspect this is due to the angle of the photo, none of the have the nice wide child-bearing hips either

. Assuming these guys are wild caught, this makes perfect sense-when fish are collected fisherman usually collect them from caves and crevices yeilding horrible male to female ratio for the aquarium trade. If you have had them for 4 years and your water quality is good I would suspect that they probably would have spawned by now. Keep your eyes peeled and you will find some, they are out there-mostly f1s that you will have to grow out, but they are out there.