The nozzle checks will show the state of the nozzles in each individual channel. But not so the purge pattern, at least not the way that you printed it. That way of printing will mean that each bar in the purge pattern will be a combination of channels. I can explain why in detail if you like (printer is CMYK but presents to the OS as RGB), but it's going to be simpler if you just trust me on this.
The only way to have each bar in the purge pattern represent one ink channel is to follow the instructions in those two links. Both involve printing using QTR in what is known as "calibration mode" - you cannot do this using the Epson driver, or by playing with the printer's settings. The first link explains how to print the ink separation page in calibration mode. The second is doing essentially the same thing, only using larger versions of the ink separation page, some of which target single channels.
The ink separation page and these special purge patterns may look really strange and it's not obvious how they work, but believe me when I say that when printed using QTR in calibration mode, then each bar or column will be the result of printing with a single ink channel.
In short - read the links.