I have a Canon 950i which is about four years old or more. Lately it always prints poorly (black print looks yellow for example) on the first effort and the only way to get a decent print is to execute the "light cleaning" maintenece. I have also executed the "deep cleaning" but to no avail. Every time I try to make a print after the machine has gone unused for a day the print comes out as above. Why won't the printer remain "clean" and what else can I try to solve the problem?