I can see why you worry Debbie - so much goes wrong as they get older - but is is all normal aging things - if you know what I mean? If you did not have the testing done, you would likely not even know these things. My RB Ernie developed early kidney problems when he was about 12 years old. I knew I would not do life extending measures and so chose not to take him back for geriatric followups. He lived to be 17 years old and died peacefully of kidney failure - as I saw all of the signs. Looking back, I am glad I did not do all the workups and preventative care because I just would have fretted over all of it.
I don't mean NOT to get Tubby the best care you can, I am just saying that the declines are all normal and to be expected.
Hope that all came out like I intended - I meant it to be realistic and comforting!