Metal halide help

Can someone help me with my metal halide issue? this is a DE 250w dual MH fixture and ballast. the ballast had to have 1 capacitor replaced but it does this on both outputs so ive ruled outthe ballast. the bulb is a 20k bulb that ignites, fires up and does just fine. but then it gets pretty bright, much more than i think it ususally should, and starts to flicker. i noticed the light color changes from the nice deep blue to a sharper white when this happens. it makes the ballast hum then goes out. anyone have this problem before? this bulb is also 3 months old. See video for details. (will post asap) Video is on facebook page. cant upload here

Didn't look for the video. If it's the correct capacitor then it's probably a bad bulb. Easy way to check is to swap positions of the two bulbs. That will tell you whether it's the power supply or the bulb that's defective.