The parameters are all good and stable, but they don't seem to get bullied, and then again I also don't watch it 24/7.They could be getting ill. Or they may be being bullied by the dominant male. I assume your water parameters are fine.
It's not that the color is kinda faded like they are juveniles, but more like it is "washing away", if that makes sense. Look at the picture where it has only 1 cpd clear in the picture and the other one blurred. Towards the back it is like fading to white, it doesn't look normal like discoloration due to being juvenile or stress. The 7 CPDs have been in this tank for about 2 weeks.I can't tell from your images. But if I had to guess, in your second image, the male is on the right and the two in the left foreground are females. Are these a new acquisition or have you had them for some time? Males are strikingly beautiful...vivid while the females are more subdue. I discovered when keeping them many years ago when they first hit the market that all of them looked the same upon delivery. They were juveniles. As they aged, the colors really developed.
They are adults, but not old. The water parameters are:Sorry for the delay in response...hectic here!
Make sure I have this correct:
Your CPD were obtained as adults
Now seven-weeks later, two of them are fading in color.
The other five are fine.
If the above is correct then I am going to make a guess that the two losing color are ill or are old.
I base this on the shape of their bodies and color. Look at the one on the right: The eye seems to be protruding and the body looks somewhat emaciated. The one on the left's body looks irregular if you follow the shape from the mouth to the dorsal fin.
Of course I could be fully wrong.
What else is in the tank with these fish?
How big is the tank and what is filtering the water?
You mentioned the water parameters are good. What are they? Hardness?
What do you feed them?
The hardness is good for your CPD's and little low for your Gobies but I am not one to suggest altering your water. In fact, I am adamantly against doing that. There is no way of knowing what the water parameters were in your CPD's grow out tank or vat. Just try to keep them unstressed as possible.
Back when I had them, I found my CPD's were happier in a species tank. The Bumble bee gobies were grumpy so kept them in their own species tank. Both species were tricky to feed. Live baby brine shrimp is a surefire food for your CPD's. Just turn off the filter when feeding and do it in small dosages. Use an eye dropper. Try small pieces of frozen blood worms too. Since you live in Texas, you should be able to get your hands on some daphnia, which they love. It is simple to culture too. Are the fading colored fish eating? What is your water temperature?