it could be their treats, it could be the water it could be a virus causing the infection.
theres nothing in RC that would realy cause a UTI...least nothing i can think of, ive been feeding RC chi and mini to the chis for almost 2 yrs now with absolutly no problems
most UTI's are bacterial and USUALLY travels UP the urethra from an external source. since dogs dont whipe, its rather unlilkely that theyve transfered bacteria from their feacal matter into their urethra, so id doubt it would be the food, its more likley bacteria in their water.
id give both food and water dishes a VERY good wash out,, if there plastic and have any kind of scratching throw them out and buy new ones, stainless steel or ceramic work best, small scratches in plastic habour bacteria.
if you have ceramic or steel id use a bleach solution then let them air dry then re-wash. if your using plastic and cant find any scrathes and want to keep using id again suggest bleaching, letting air dry then throughly wash again.
all preferably at HIGH heat.
hope there feeling better
and welcome aboard Ruby