With no symptoms of bradichardia, heart rate of 50-52 is good and is probably not associated with your tiredness. Sounds like you have a strong healthy heart.
If you don't have dizziness or fainting the HR works for you. A resting HR under 60 is low, but like blood pressure, low is good unless it causes some problems. I do not relate being "tired" with a low HR.
In the absence of any symptoms I'd be happy with the HR. If it goes below 50 you could benefit from a heart check-up in my view. If you haven't had a physical medical exam lately, now could be a good time, and a good time to talk about your HR.
Again, from the limited information you posted, I'd say the HR is right for you.