I'm new here and got some problems of my own, but I would think yours has something to do with the capping station and/or waste ink pump or the lines between them and the waste tank. A good test is to do a head soak by putting some cleaning fluid in the capping station and then do a cleaning to pump it all out. If the fluid leaks over the top of the capping station then the capping station may be bad. If the fluid doesn't drain all the way then it is likely the lines or the pump. But the easiest place to start is to check the waste ink tank and make sure it is not full and is inserted properly.
Show the picture of the black smudge; blue lines, and a nozzle test or its attemp
individual pictures please - so that we can clearly see what is going on
We are trying to imagine what you are seeing