Color Shift

I had a color shift start this week on my latex 315. We don't print 7 days a week, more like 2 right now. All the sudden my reds and yellows are off. Yellow is washed out like its sun faded and reds are more pink. Those are the only colors having a problem SO FAR. Nothing changed in software or firmware, I think it's ink related. I don't print a lot so I haven't even replaced an ink cartridge yet, but we've had it 18 months and I know inks expire. I have a few newb questions... 1) Have any of you encountered older ink going bad like this and losing its pigment before their expiration date? I tried shaking them all pretty violently for 20 seconds and reprinted, nothing changed. 2) I'm going to buy a yellow cartridge to see if that fixes it, but I'm wondering if color fade could be a result of the yellow print head? There's no quality drop, it's purely lack of yellow colors in anything that's pure yellow or red/orange. But could a printhead do this? I cleaned them all and they are working OK. 3) I've never replaced cartridges so when I put new ones in do they need to go through a break in phase like running a color calibration or will it be good to go right out of the box? Thanks in advance!

Hi @TrulineGraphicsLLC, Looking at your comments I would the first to perform a nozzle check, as well as check and clean the PH. Print also a plot of 5 meters with a big rectangle in composite black. Afterward, do a color calibration. Bear in mind also that expired inks can lose their properties and provide a low printing quality. If after all these you still have issues, I suggest contacting HP support.