My boy benji had a URI exactly the symptoms that you have described, I went to the chemist too get the senega and ammonia for Benji but it just didnt clear things up for him and ended up having too take him too Albany Creek, I really hope you have more success with the Senega/Ammonia then I did.
Thinking of your piggy. I tried my boy on that for 4 days and it wasnt working as well as I hoped but the vets said that he had too have Baytril and it has cleared everything up, I was lucky enough that Benji still wanted too eat and only just got slightly runny poos at the end of the treatment and nothing else.
I think if it comes too going too the vets, the antibiotics will nip it in the butt very quickly and you will have your precious one back too good health again.
All the best.