One key diagnostic you need to perform is a nozzle check. This will
tell you what has happened to the other ink colours as much as indicate
if yellow is polluting other nozzles.
You can run a nozzle check from Printing Preferences > Maintenance.
Once it has printed you should (normally) see a sort of stepped grid pattern similar to this
you can scan or take a photo of the output and the post it as a follow
up it'll then be possible to get a bit more of an idea of what could be