What's going on with my Tetra fish?

I have a Gourami fish and a Buenos Aires Tetra fish. They are both eating and swimming around and seem happy. I got them about a week and a half ago and I've noticed that the Tetra's fins have become extremely pale. When I got him, they were bright red but now they are barely even pink. Just 2 days ago the color started to come back, but they still aren't red all the time. Is there something wrong with my fish?