What causes high diastolic pressure?

I’m 27M, 6’0ft, 225lbs and eat relatively healthily and exercise almost daily. Perhaps on the verge of overtraining.

I was diagnosed with stage 1 hypertension back in March 2023 and I have been on 25mg of chlorthalidone daily since then. My systolic is usually always elevated but never much of a concern. However my diastolic pressure recently has been quite high. As of September 2024 it’s been always above 85. Highest it got to was 100 but I was on a verge of a panic attack, it went down to 85 after 5 mins of chilling out.

What could cause high diastolic but relatively lower systolic? The only factor I can attribute to is stress and anxiety. I’ve had ultrasounds of my kidneys and renal artery and they all look normal. I also have a right bundle branch block but it seems to be a congenital issue.