You’re a wonderful daughter and any parent would be proud to have one like you! Maybe now after all these years the stress is indeed taking a toll on their mental health and some depression may be setting in. Forgetting things is just one sign though. Are they having trouble sleeping? Waking up early morning and unable to go back to sleep? do they feel sad through out the day? Do you think they have lost interest in things they used to find pleasurable earlier? These are just some things that may tell you if this is something that needs expert help.
Other than this, try and spend some quality time as a family. Plan an outing where all of you can really connect. Maybe a place where they took you as a child or something? Nowadays there are lots of activities for elderly people (although your parents are still young) that they can engage in together. Maybe you could find something in your city? What I’m trying to say is, we need to get them moving…active…out of the stagnant life that has come to a stand still. They need a change. Something fresh And on top of it all you can even opt for family counseling where new avenues of communication between all of you can be opened. If you need help with finding someone, just let me know.
All the best!!