I don't realy know anything about flowerhorns but I do like the look of them and some of those you posted are stunning fish - I think it was the last one you posted I liked most. I find I like their nuchal humps - it suits them - while in many other fish I don't. Having said that, I think big fish with nuchal humps have grown on me ever since I discovered the osphronemus gouramies
Are they all yours BTW? I look forward to seeing more pics
Having said that I know nothing about them, I do know that vertical bars on many cichlids mean stress (eg: discus). I did not know flowerhorns could display stress bars though
Anyway, stress is not necessarily water-quality related. A fish can be stressed because it's spawning, because it's lonely, because it feels uncomfortable, doesn't have enough room to swim, doesn't have enough hiding places, isn't getting the right foods to meet it's nutritional needs, vibrations from a stereo/tv or people walking/running passed, wrong temperature, fluctuations in any of the many water parameters (both those you can measure and those we tend to over-look), wants to spawn, is ill, is injured, is hungry, is in an overly-bright (or dark) environment, cannot sleep the necessary amount of time during the night (yes, they need to sleep) or the lights are on too long/direct sunlight and so on. Obviously, there are plenty of reasons besides detectable ammonia/nitrIte levels or high nitrAte levels to cause a fish stress.
As for her yellow coloration, it seems normal for the colors to intensify during spawning. cracker said her colors could be even brighter if you fed her the right foods.