Are Aqualine 175W 10Ks often different in color?

[ReefDream]

I noticed a very odd thing about my 175W Aqualines when I recently changed the bulbs. While the old ones were the same color, the new ones were not. One of the new 175W bulbs was vastly more yellow than the other although the two were bought at the same place and looked identical in every other aspect. The old bulbs did look slightly different in that they had different markings on the bulb, but they had the bluer color. Of the new ones, I would estimate a 4000K difference between the two. Maybe this was a freak case. I don't know. Oh, and I did switch ballast to make sure that wasn't it; it wasn't.

Has anyone else had this happen to them? If so where did you buy from? I bought from an Ebay guy that runs a store called Seastar Imports or something like that in Florida.

[ReefDream]

Oh, one more thing: I swapped out the yellow one with an 11-month old one that I used a year ago. I could not tell any difference in color or intensity between the 11-month old bulb and the brand new one. And the 11-month-old bulb has a totally clear arc tube. The other 11-month-old bulb that I ran with that one had a cloudy and black-ended arc tube. Those two bulbs were run at the same time by the exact same model number pulse start ballast! Do the bulbs age that differently too?

[lllosingit]

I bought 2 brand new AB 175 watt bulbs and had 1 that was new in the package but purchased a year ago.
The newly purchased bulbs looked very yellow compared to the new bulb I bought last year.
Besides the different color I also noticed the old bulb (white color) had the AB label on the end and the new bulbs(yellow color) had them on the side.
It took about 3 weeks of running time for them to match,Now I can't tell them apart .

[ReefDream]

The two new ones had the label on the side. The old ones had no label on the bulb at all. Of the identical newer ones, one was much more yellow and one was much more white. I use the hand-test to tell the most easily the difference. I just put one of each of my hands about 5 inches below each bulb. If there is a yellow cast, my flesh tone (I am caucasian) really points it out drastically for some reason. Of course you can tell it also in the tank, but the hand test is much more drastic and easy to see.

I never even considered that the color might change in the first weeks. Maybe I will try that. The new bulbs have been running only five days.

[ReefDream]

One more thing: I looked a little closer using the hand test, the 11-month-old bulb is definitely quite a bit dimmer. It isn't so obvious in the tank, but if I use my hand test, I can easily tell it's lost about 30% of the light intensity or so.