Thanks everyone. I really needed to hear some good news because it just seems like at least one of my furkids always has something wrong with them. Now if I can just get Sunny's feline acne cleared up then everyone will be fine.

Yes, the Royal Canin S/O prevents both the struvite and the calcium oxalate crystals. I feed them both the wet and dry food and I'm able to maintain their weight by feeding them each 1/2 cup of dry food a day and they each get a little wet food 2 times a day. I feed them 4 small meals a day,2 in the morning and 2 in the evening, so they think that they're getting more food. I also give them each 6 feline greenies treats every evening. So far this feeding schedule is working for me.