Having soft erections is a form of erectile
dysfunction, as you know, and this can happen as we age.
Medication can widen blood vessels and leads to firmer erections. https://www.medicalnewstoday.com/articles/ed-cures-for-seniors It sounds like you pay attention to your health which is great. You want to rule out that first as the underlying cause. Treat whatever issue there is. If you've done that, then it is time to ask your doctor for help.