R1900 - misfiring nozzles or alignment?

InkjetMall Customer Support Printer Maintenance & Cartridges
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This is a follow-up to http://www.inkjetmall.com/tech/showthread.php?921-R2880-can-t-maintain-a-good-nozzle-check&p=5887&viewfull=1#post5887 . I started a new thread as the current problem with this printer now seems to be different.

Having cleaned the printer and replaced the suspect MK cart, I had no gaps in the first nozzle check, but had signs of misfiring nozzles.
There was a thread about this on an R2400 recently and I also read the support page on this topic.
I printed a purge pattern but that didn’t help.
I did a head clean, and that helped a bit.
At this stage it looked like there could have been some head mis-alignment. I did a manual alignment. It wasn’t that far out, but it may have improved things a little.
I think that there are still some slightly misfiring nozzles.

Attached are two scans of nozzle checks. The first (on EEM) was taken before the head alignment, and the second one (plain paper) after. Both are after the second head clean (the first clean being the mandatory one after refilling the carts).

I’ve read the misfiring nozzles help page http://www.inkjetmall.com/tech/content.php?167-Evaluate-a-Manual-Nozzle-Check-to-Determine-the-Health-of-Your-Printer , but I’m not sure what to try next. I am reluctant to try more head cleans without some likelihood that they would help. Piezo ink isn’t cheap. That help page says to clean the printer, but I’ve already done that, except that I didn’t push flush through any of the channels as it didn’t seem to be needed. If I am going to trigger a head clean, is it worthwhile pushing some flush through the MK channel?

Questions:

  1. What would you advise as the next step, given the above and my desire to minimise wasteful head cleans?

  2. The manual head alignment print was fairly faint, and I had to print on coated paper to read it with confidence, using a loupe. Will an auto head alignment work on the R1900 with Piezo K7? Is the shade being used dark enough?

  3. Is it just a coincidence that the misfiring nozzles are on the same channel - MK Shade 2 - as I seem to have issues of leaking and had to replace the cart?