What Causes Sudden Weakness And Nose Bleed?

Hi, I experience a sudden & severe weakness this afternoon while washing windows. I had a nose bleed. I came in & took my BP it was 93/68, My pulse was 101 & my temp was 95.6. I'm a 69 year old woman living at 10,000 feet in the Co. Rocky Mtns. & am a vegan. Any ideas for this. It's never happened before.