I would like to affirm what donnamt posted about guilt & feeling we have let down our buns.
I suggest that you imagine someone else who is as devoted to their bunnies as you are, may be someone you know. Place them in the same situation you were in with the same knowledge & state of poor health you had, with the bunnies who passed on. Look at how the situation developed, the information available at the time. Would you blame them for failing their buns?
If the answer is no, then why do you treat yourself differently from the rest of the world?
If the answer is yes. IMO At the end of the day we can only do our best, it's impossible to do more. We all have limitations/constraints too.
Fact. In bereavement, after the shock, it is usual to feel a mixture of guilt & anger although 1 usually predominates. Until these feelings are sorted out, we cannot progress to resolution/healing. Until we have reached resolution, we will react to further episodes of impending/feared bereavement with the full force of the past feelings together with the present = overwhelmingly painful.
Similarly it is common when prolonged drawn out suffering ends in death, to feel relief. The relief is 2 fold, for the patient released from suffering, & relief from ones own emotional exhaustion & pain caused by watching someone you love suffering yet being helpless to relieve it. There is nothing wrong with that - no need for guilt.
In the above, I speak as a fellow suffer. I've no psychotherapeutic training.
So to Badger.
XR of lungs sometimes doesn't show disease even when it's present.
Bunnies have small lungs in comparison to their size, so they can't cope if a relatively small part isn't working.(We hardly notice it if we lose a whole lung) Of the illnesses which can be treated, there may be more.
You are thinking of pneumonia. Zithromax is licensed for human use. The only microbiological information I have found so far, pertains to bacteria which cause disease in humans. Rabbits may get human bacteria but just as commonly get totally different bacteria.
There is congestive cardiac failure.
I do not know whether rabbits can get a disease called fibrosing alveolitis or something similar. This may account for why Lionel was prescribed steroids.
True allergy - bronchospasm is rare in rabbits, but can happen.