I don't know if they need to outright sell, since their biggest trade chips (Semein and Ray) would both net the Jays a compensatory draft pick if the team qualies them and they walk in free agency, but there's no way I want to see them go shopping for rentals.
The bullpen obviously is an issue (and the bullpen management to be frank), but so is this team's ability to hit in the clutch. Seems they only ever win blowout games. I don't know if there's an in-season fix for that.
Actually, on that last point, if the Jays can make a move to bolster the bottom of the order, they should. They have a lot of aggressive hitters in the back half that aren't great at getting on base (Grichuk, Gurriel and lately Biggio).