25 days post iud removal/insertion. no issues w/ first iud. no pain so far with second iud, after initial insertion anyway, had light period for 5 days. today, 1 day after end of period, i went pee and had a small gray tissue matter on the tp. why?

Probably unrelated: It is not clear from your description what this may be but it is not something that we associate with IUD use. If this continues to be a problem you would need an exam. In any event it is good practice to have an exam a month after IUD placement to confirm that it is still in proper position. The risk of spontaneous expulsion or displacement is increased in the first month.