I have done as you suggested and thre is no difference. I have been using photo paper as well, not Epson, but Kodak. In the past all has been fine, but today, it is rubbish! It will not print true colour from a Foxit document that is in colour either.
I have to confess that I have never been 100% happy with the Epson from a quality or speed point of view. But when my HP went up it I had no choice but to continue on with the Epson.
I've now tried head cleaning & checking alignment, but it is having no affect.
All the colour cartridges are about one third full with the black being three quarters full. The only test page that comes from the Maintenance is just a few lines printed from each colour which are angled but in a single line. i.e each colour is 9 lines deep by 1" long angled. It hardly seems a good check since they are quite pale.