What cause brown , rusty brown, then bleeding red with clots of tissue 4 days after plan b ?

Plan b bleeding : This can be the normal hormone withdrawal bleed after taking any hormone, including plan b. Always check a pregnancy test after taking plan b at the time that your next normal period would be to make sure that you are not pregnant.

Withdrawal bleed: The bleeding should taper off, much like a period, after a dose of hormones was given all at once.