yellowing water?

[galeas]

so I've noticed my water is turning yellower and yellower. I've done two water changes in the last month, turned my protein skinner on a higher setting and added new cleaning crew. My fish are still happy it seems, eating like pigs and swimming around.. my yellow tang seems like he might have some ick as he wont leave my cleaner wrass alone. If anyone has any suggestions or tips please help as i would really like my water to be clear again.

Forgot to add its a 90g tank approx 2.5 months old. All my levels are at 0 on my last check which was last week (will be doing another one soon)