What Causes Low Diastolic Pressure In Women?

Hi I am really into fitness and workout 5 days a week. My diastolic pressure was 69 today and thought that number was low, I ve never really paid attention to the bottom number until it was called to my attention,so seeing it low was cause for concern. I am a female 43 years old and top number is always around 102/108..... Today it was 111/69. I assume I m fine just curious.