Thanks for the additional information Christopher. Instructions for uploading images to this forum can be found here: http://www.inkjetmall.com/tech/content.php?152-How-to-attach-images-to-this-forum
A channel should not be completely blank after just a day without use, so I suspect something with the printer or cartridge isn't providing a tight connection, which is causing the channel to lose pressure and/or ink prime, resulting in the blank channel. How long did you use the printer with Epson inks? Did all channels work well/consistently with the Epson carts?
Your humidity levels are very low, and the combination of hot/dry conditions (especially dry) will cause drying and issues with your printer, ink and papers. Other than low humidity and high temperature, it sounds like you are doing everything right and haven't done anything like run the cart dry or left the vent plug in the cart that would cause obvious issues. Although it sounds like the cartridge is working normally (no obvious leaking, ink in the exit chamber, and ink flow returns after a cleaning cycle, then remains during printing), it may be worth trying a new VM cartridge to see if that helps (with ink, I don't see the need for PiezoFlush at this point since the flow returns easily, and the printer is still fairly new). Other than that, I recommend increasing the humidity in your printing environment by using a humidifier (to counter act the results of using an AC, which is sucking the moisture out of the air). In our print studio, we run ACs' in the hot/humid summer months, and humidifiers' in the dry winter months, but monitor the levels daily, and maintain proper levels by balancing the AC/humidifier use (especially in the spring and fall, when it's in between moist/dry and cool/warm, depending on the day or even time of day).
Please keep me posted, let me know if you have further questions or there's anything else I can help you with.
Best regards~ Dana