Tiger barbs color change?

[NormsAquatics]

My glofish have slowly become more silver and the emeralds are developing a light spot between body and tail. My question is, is this natural with age? I've had the larger barbs for around 2 years and the smaller barbs since Feb of this year. There's also 2 bull heads(local stream) and 2 Chinese algae eaters(1 too many).

  I've tried api phdown with zero success, hoping that's the issue. I found a rock with lime and removed it yesterday. It was in the tank for about a year. There's been no die off or behavior changes. Water temp is 78-84. My thermostat is digital and is terribleness.

[Colu]

The colour change could be due to stress as your trying to alter your pH also Chinese algae eater can attach themselves to side of fish and eat their slim coat