im so sorry for your loss
did they check the heart?
my sasha was fine then one day she was really weak so i took her to the vets and they said her heart was fine but thought it might be her lungs but when they did a xray they could see her heart was enlarged and that was the problem, even with meds she died as she just didnt take to them.
i wonder sometimes if an owner of a yorkie is told its a collapsed trachea that is causeing the coughing was its a coomen thing for them to have when really they have a heart problem, i noticed someone else on here said there dog was very restless, well thats just how sasha was as if she laid down she had trouble breathing due to fluid in her lungs.