, 50 is still high, unless you have a lot of plants I would keep the nitrates bellow 20. Your water is too dirty and your fish are living in their own waste so that is why its doesn't look so good.
Target nitrates below 20ppm with water changes using temperature matched dechlorinated water. When you say on par, do you mean ammonia and nitrite at zero consistently?
Are those fish genetically modified for colour? I'd go with big water changes to get nitrate below 20ppm, and keep it below 20ppm, give it a week and see if it improves.