Diapers coming out smelling

Whenever I wash my diapers, and other baby clothes for billing purposes, they smell. Just faintly of pee. Not ammonia or barnyard. Sunning isn't really an option because I live in an apartment. But I lay them outside when it's warm and sunny, no direct sunlight though. No one else in my family can smell what I am smelling. But even the clothes have it. I know there is still some detergent built up because I'm using liquid tide, but I don't even smell the tide in them. I wash twice on hot and heavy. Then do another cycle with no detergent to help rinse. I feel like my apartment washer just don't wash. Nothing agitates so I don't think they're actually clean. What do you guys think? I would just hate to burden my MIL to come and do diaper laundry all the time.