Keep the exercise up if you can, it sucks to get older and have things break down, so the more you can return to fitness the better, it may help as you age. Also with a big weight and body loss it takes time to get back to where you were. Next doc visit if you have not done so yet, ask about your B12 vitamin levels, being a vegan, and the changes your body has gone through make sure they are adequate, it will help any nerve damage changes heal supposedly and also help with some brain function according to street lore, but ask the doc first.