I can see what you mean, but the occasional slump is to be expected. Your bigs may knock one down now and again, so do mine. My PF with average JS and pitiful JR has had 2-2 3fg games. Like other people said, they often get open looks.
I've taken a look at your team stats and all your SG's have pretty decent 3pt %. In fact Ortiz has a very good %. So you can't expect them to deliver every night, even when they're playing opponents with low OD. In the end we just have to look at statistics :P