Hello Dr. , My Gf Has Low Blood Pressure At

hello dr. , my gf has low blood pressure at some times, since some years she is getting blood in motion (stools), there are no external sight of any hard skin/bulging, yesterday she went out in hot sun, sudden climate change. she got blood for 2-3 times. i am worried.

what would you suggest:
need colonoscopy, or diet change or climate issue... ?
an MBBS dr. said may be due to heat in body.. and climate change...