All inkjet printers can suffer from "drying nozzles". All such printers have a "parking/cleaning" station for the print head that is "supposed" to seal the nozzles from ambient airflow between print sessions.
For black text/line drawing doc printing, a laser printer is less trouble and can...
Those KINDA look like OEM carts to me.
Anyone else care to chime in?
If they are not OEM carts, DO NOT USE THE YELLOW CART!!! REALLY!!!
If it is non-OEM, then you run the risk of "yellow jello", clogging that print head channel.
Use the carts marked "start-up" first!!!
Assuming the print head was cleaned of all ink in it's passageways, flushed with distilled water, dried, stored correctly (dry), I suspect it would have no issues upon re-installation and a deep clean cycle.
I would try a good soak of the printhead. I would even gently pressure flush the PGBK paths. If the nozzle check is OK (and it seems it is), and a known good cart is used, there must be starvation of flow to the PGBK nozzles somewhere. That could be in the internal passageways between the...
I would allow the printer to just sit a day or two, which typically clears air-binding in my Artisan 750. I believe the air dissolves into the ink, but who knows?
I would not use tap water for a "final rinse" of a Canon print head. The unknown amount of dissolved solids will potentially clog the fine nozzle orifices upon drying. They are REALLY small.
You can use tap water for rinsing, followed up with a final rinse with good, distilled water.
"I'll get a substitute for Windex (Glassex, they don't sell Windex here) and see what that'll do. "
I don't know the formulation of Glassex. Original Windex contains a small amount of ammonium, which is critical to performance (IMO).
Given all of the above, I would say you have an issue with the waste ink removal system after the "parking pad". Either a clog in that system, or a poorly operating pump. I would flood the pad with a standing pool of Original Windex, let it sit for a hour, run a cleaning cycle, and re-inspect...
It does not look good. If you have cleaned the contacts, try again with a pencil eraser. Else, your print head is probably "toast".
Have you been utilizing "quite" or "night" mode in the driver? That can potentially reduce thermal duty on the print head.