Angelfish acting strange?

[TML182]

Hey guys,
I have a veiled angelfish thats roughly 3.5 inches (top to bottom) that has been in my 50 gallon tank for 4 months. Everything was ok unil recently when i removed 2 koi angelfish that had grown up to be quite aggressive to all the other tank mates. It now simply stays near the bottom of the tank rarely moving much.This angelfish isn't showing any signs of physical harm and the other 2 zebra angelfish are acting completly normal. The tank is a moderatly planted tank. Just wondering if anyones had any similar experiences or ideas what's causing this?

 

[tyspot1000]

Do the Zebra angelfish happen to be a pair? What Are you parameters?

If the Zebras are a pair, that could be a problem. Most of the time the Pair will pick on the Lone angelfish left in the tank, causing stress on it. If you see any bullying, remove him so no futher damage is done. Its recommended to have even an amount of angels in the aquarium.