Have you had a soil test done? It's the only way to confirm and recommend the best solution for a soil deficiency. Your county extension office can do one, mine was $15.
In the meantime, does the plant feel dry and crunchy or limp? Smell the roots. You can usually smell root rot. Is the soil draining? Scratch a damaged branch and see what color it is inside. White or black is probably a fungus.
Do you have a magnifying glass? Some insect infestations can be hard to spot. Use the magnifying glass to look at the underside of leaves. You may find webbing on the plant, an indication of spider mites. You can wash them off with a direct stream of water. But eliminate the fungus and overwatering options before you use more water.

Mine ALMOST croaked too. It had a good run. They don't live forever. I don't recall what the leaves did but the wood at the base just seem to rot away. Happily she is back from the dead. Its smaller than in her glory days but still popping out flowers like crazy. Mine is about ten years old. I cut it back to the ground in the fall thinking I would just buy a new one. Its by far the best rose I have ever had. I can't recommend it enough. Its in part shade back there. Not ideal conditions for a rose. If it only didn't have thorns it would be perfect. All the others just deteriorate in one way or another within weeks or months. Most don't survive the winter. I got two more for the front of the house but those are "double knockouts". I would have bought the old regular one except I can't seem to find it so I took a chance. I am skeptical they will do as well but I am trying it.