Hope someone can offer some advice. I noticed yesterday evening my fish had some dark red on his dorsal Fin, and also his tail fin near where it meets the body. Not sure if this is a color change or something to be worried about. Water test shows no ammonia or nitrates. P.H between 6.50 and 7. Fish is yellow and this new color is red. This is the best picture I could get today. This happened suddenly as I did not see this change two days ago.