So my Clown and my Tailspot Blenny have recently been stretching their mouths wide a lot the last couple days, around 1 or 2 times every couple of minutes. I'm worried that when they do this, they're sick, but after researching the topic, it seems that I might need to do a water change or something. The tank is ten gallons and around the same day they started doing this, I put in a large amount of freshwater because of evaporation. Do you think that I just have low salinity and high nitrates, or is there a parasite eating their flesh?