As per the BJCP troubleshooting guides, popular causes of astringency can include overcrushing, oversparging, too high a pH (over 6.0) or too high a temperature (over 170f). It sounds like you have confirmed your crush, or at least are trusting the crush from your LHBS, and have confirmed your temp. If you are doing BIAB, I'm assuming you are not doing a sparge (dunk sparge in another pot?) or mashing out for too long at too high a temp either? In that case, the only thing left to check from this short lost of possibilities is the pH.