There are a few things that can cause this. First of all, though, stop running head cleaning cycles. These are only for if there are clogged jets that aren't printing. It has the effect of running ink through the heads and which will only be dropping more ink where you don't want it inside the printer.
I don't have an Artisan 710, but on the Epson printers that I do have there is sponge material all along the platen under where the print head slides back and forth. On my WF-7720 I have had the exact same issue you are having when the sponge gets overloaded with ink and expands. It bagan to make contact with the paper, and this ended up causing it to get pulled out of where it was tucked and causing ink splotches.
I also have seen the same type of effect when using very thick paper or card stock. It can happen on regular paper when it curls and scrapes the print head as it goes under it. But it is more common on card stock because the print path bends the paper and card stock may not bend quite enough to prevent it from scraping the print head.
And, lastly, it may indeed be some lint or small ink-soaked paper piece that is caught somewhere.
Unfortunately, there is no magic solution to any of these. You have to open your printer and look. Look all along the paper path, especially the platen. If there looks to be any sponge material out of place, tuck it back in. A good flashlight and a dental mirror (or any mirror-on-a-stick) will be your friend here to look in places you can't get at.
