Black Print Banding

[D.a.n.i]

I have a Canon iP8750 printer and for ages it’s been fine at printing black prints with white text on. Recently however it’s been putting darker black thickish lines across the top and bottom of the prints and I’ve tried everything to fix it but it won’t get better.
I’ve cleaned the print heads, cleaned the roller, done print head alignment. I’m not using just black to print, it’s a mixture of CMYK.
Could anyone help or have any ideas?
Thank you

 

[D.a.n.i]

This is what the prints are looking like