Sure they could, but would it really be worth it to them for the damage they would cause and the cost they would incur?...1000lb can't do much damage to a facility buried in a mountain, not much at all can. With few assets like the Heron they could do only limited strikes on a handful of targets, the Iranian nuke program is much bigger than that.
Some say they may view Iran as enough of a threat where they would be willing to incur a lot of wrath from the West even for a strike that only sets the Iranians back a few years in their program.