Your auto nozzle check from top to bottom shows the shade 2/cyan (2nd from left) position lost density, and got darker after a few cleaning cycles.
The reason your printer kept telling you nozzles are clogged with the auto nozzle check, is because shade 7 is so light the printer's sensor can't see it, so will think/report that channel is clogged/missing (but I can see it's there).
The second photo you attached is an alignment pattern, not a manual nozzle check, but I can see what I need from the first four channels of your auto nozzle check.
The cause of your solarization/ loss of density is actually in your shade 2/cyan channel, so it's just a coincidence that it happened after you changed black inks.
After reviewing your order history, I see you bought a 110ml bottle of WN#2 ink last month, but the last time you got WN#2 was in 2013 when you bought a set of 110ml WN bottles.
Please tell me, are you using WN#2 ink from the bottle you bought recently, or from 2013?
What is the lot# on the WN#2 ink bottle you're currently using?
How often do you use the printer vs. how long does it sit unused?
How often do you agitate the ink cartridges?
Do you always shake ink bottles before filling/refilling carts?
Please let me know so I can help you get past this and back to happily printing.