my wifes weinerdog

(male) has uti trouble. she used to feed Pedigree but the vet said that it was the cause because it was either too high or too low(i forget) in acidity. so she switched to Purina products and it was fine for almost 2 years. now its happening again. our vet blames the food again and wants us to use only their $30 for 10lb food

. im not saying the vet is wrong, i bet their right, but i also bet that another brand of food will work as good as theirs. i feed Diamond and on ocassion Sportmix and never had any troubles with my males. what would you (Doc S) recommend. oh....we also use methigel when he has this trouble. any tips would be much appreciated.