Ok I asked this a while ago and got an answer way off what I asked. My tank is fine, everything is reading out to be perfect such as the salt levels in the water. At the front part of their head, right by their mouth is a black spot which looks like it might be the start of a stress line? Q: Can a stress line start out solid black or does it have to go from mouth to tail before it starts to darken to black? It hasn't progessed at all since I got them, and they have had it for over a month now. No belly darkening or loss of color, so I don't know what to think?