Why did my blue tangs change color?

[lanalex]

My blue tangs were mostly blue with a streak of black going down the middle of their bodies. They have changed color where now they are mostly black with only a small section of their middle body having the blue color.

What happened? What's going on?

Help!!

 

[Josh88]

Can you take some pictures?

 

[The steven liu]

What are you feeding them? I know most Tang will have coloration issues if they have malnutrition due to lack of vegetable based food.

 

[Jeremy Blaze]

How long have you had them?

 

[lanalex]

I have had them for 6 months. The only thing I can think of is that when I got my new Taso Tang I started feeding it spinach and the blue tangs are eating it too. Would the spinach do it?

 

[Jeremy Blaze]

Why would you feed them spinach? That is a totally unnatural food for them. Pick up some dried seaweed from the grocery.