Some months i get a rubbery pink or brown "plug"/membrane discharge before ovulation. is this normal?

Discharge: ovulation: At ovulation, there is a precipitous drop in estrogen, which can cause light bleeding (which turns brown when blood cells oxidize). At age 31 you may be having higher estrogen made in your ovaries, and the drop with ovulation may cause these symptoms. Ask your gyn about low dose oral contraceptives, which will stop ovarian estrogen production.