3YR Old, Female GSD mix with constant fishy smell

My GSD dog (50 percent GSD, 30 percent other showed, 20 percent cattle-if that matters) has had a constant fishy smell for years. The Vet won't give us any recommendations. She is picky about food so changing it up isn't a big option. When I can I make chicken and brown rice to add to her dry food (she gets pro plan large breed per vet). We get glandex supplements and wipe her down as much as we can She doesn't like it but she allows us to. Sometimes her butt is dirty, sometimes her vagina is dirty. But the smell is almost constant. It's getting really overwhelming. We are getting no answers. Does anyone have any recommendations? She's not in pain, we don't think She plays well, super sweet family dog. We are desperate. She gets anal glands checked monthly when we get her groomed. She gets walked every other day, due to winter weather it's been harder for more walks from us (I can't walk her with my son because he screams in a stroller and my husband has had to work late hours and she won't walk at night). We have three acres to run in outside of walks in the park, she gets mental stimulation daily with reinforcement training with me and my toddler. I'm just trying to figure out what we could be doing. Google says more fiber, we offer options and she doesn't eat it. They say more movement and we are looking for a second dog walker (she gets professionally walked three times a week but we're adding more). Our house constantly smells bad and I'm nervous about my dog and germs with my kid (they're best friends). All blood tests are normal and vets have no concerns. I want to rip my hair out.