False positive? On two tests

Brianna

Do frers eventually get a pink line after sitting for awhile? I've taken them before and with a bfn later when I looked I just saw an indent/evap line. but when I thought I saw a vvvf line I threw it away after the 3 minutes.. looked later and much brighter pink line. on two different tests. So can frer get a pink line the longer they sit?