Odd respiratory illness

Hi I really hope you can help! Dogs details: Cody, 9y 8m old, neutered, male, Siberian Husky, healthy weight, no health issue other than the following. We noticed Cody having the odd cough every so often but it was nothing concerning. One night a few months ago, Cody's breathing became laboured. He was having to work pretty hard, was sucking his abdomen in and his breath sounded rattly. Luckily, it was early enough to contact our own vet so we took him down ASAP. Upon a vet consult, we were told he was not very well at all and it was likely pneumonia. He was given an injection of synulox and a 2-week course of tablets to continue with. The advice given was to keep him warm and rested and ensure he was getting high quality nutrition and hydration. This seemed to do the trick and he improved massively. The improvement continued until day 16 (2 days after the course of antibiotics ended) and he was pretty much back to square 1. We spoke to the vet and decided to have chest xrays done. These xrays did not show any further signs of pneumonia but he did have "marked changes" to his bronchioles. The decision was made to give him another, longer course of synulox as his improvement was so good on the tablets. This course lasted a month and again, the tablets made all the difference and he was doing very well. He finished this course of synulox approximately 4 weeks ago. He has been absolutely fine until today. He has had a few coughs throughout the day but tonight he is again, working hard to breath, he ate at around 7pm but has no appetite at around 11pm (even for steak!) and is quite subdued. His pulse rate is 70, resp rate 40, gums normal colour, still drinking ok as far as I've seen and was happy to go on a short walk, he was interested in the environment and his breathing was ok walking and trotting, I didn't attempt anything faster. His breathing returns to normal whilst he is asleep. We will be contacting our vets again in the morning but just wondered if you have any insight into what this could be? His huge, nigh on instant  improvement whilst on the antibiotics and resulting decline off of the tablets are the most confusing part. We have 8 other dogs who are all in constant contact with Cody and none of them have shown any symptoms (of this condition or otherwise) at all Money is incredibly tight with his insurance counting this as a pre-existing condition due to the mention of a mild cough at a check up when he was a pup 🤦‍♀️ so we really need to nail what this is and how to get our boy better ❤ Any help is much appreciated!

Hello!  Your vets sound to be in the process of trying to find the cause of Cody's problem and, as people who may have examined the patient, seen radiographs, tried antibiotics and so on, their shortlist is likely to be much more to the point than mine.   I don't know whether various parasites such as lungworm can be ruled out, for example - or whether they are satisfied that they have ruled out bacterial disease as a cause, or why the symptoms might recurr when the antibiotics stop.   Could this be down to need of a longer course, or might there be a foreign body for example?  It sounds as though it is time for this conversation. Never be worried about bringing up financial concerns with vets - it is a common difficulty and they should help to use any available funds to Cody's benefit.  'What would you do.next if you only had X money to spend?'  This may include talking over the information with a specialist for a distanced second opinion for example, regarding the best way to move forward from here. Best of luck.