Oh, I'm so sorry to hear of your loss.
You must miss her so much. We lost Halley, our 3 y/o Pyr to bone cancer last year. It was misdiagnosed by the vet twice as a foreign object in her paw. They did surgery and ran two long courses of antibiotics, but no x-ray.
We were new to town and this was our first visits to this vet, so finally I called Pyr Rescue to ask for advice. I credit a wonderful woman at rescue for suggesting an x-ray. I had Halley in the next day for the x-ray. It was bone cancer and already too late and she had only a slight limp and intermittant at that. My experience is that these big paws don't always show any discomfort until it is too late. I'm so sorry that you lost your Anja. I hope that my Halley met your Anja with a big play bow.
Regarding your poor boy, Daisy, our Golden developed terrible vomiting & diarrhea the last month of Halley's life and for a few months after. Despite a couple of months and lots of visits to the vet (new vet by then) for tests & meds, and a diet of rice and chicken baby food, the problems continued until the vet diagnosed either IBD or food allergies (he wasn't certain) and put her on a duck & potato kibble and she' been fine since. One of our son's has severe food allergies that worsen when he's sick or stressed, so we've wondered if stress is what caused Daisy's problem to develop. In the last 2 months we've adopted 2 new adult Pyrs and now Daisy can occasionally eat a treat (non duck & potato) and digest it ok. The only thing that's changed is that she is happier now with her new siblings. If you haven't, you might try taking him to the vet to check for giardia or other things that are treatable with meds. Then if it continues, you may want to consider an allergy formula food like duck & potato or sweet potato and fish and see if he does better on it. Also, all of our dogs love the duck and potato (dry as well as canned), so it seems to be very popular. I'm sorry that this is so long, but we've been through something similar and I really sympathize. Please give your boy a pet & a kiss from Daisy & I.
Also, if you stay on BPO I think that you'll find lots of comfort here...I know that I did.
Please keep us posted.