The dark side of the Force was clouding the Jedi's minds and hampering their abilities. Yoda discussed this with Kenobi and others in the prequels. Also a Jedi is not always in tune with the force, they can be distracted by emotions and stuff and not be able to let the force guide their actions. It's pretty basic Jedi knowledge.If that were true how did jango gun that jedi off the balcony, his blasts are way below lightspeed.But Jedi could 'dodge' real lasers, because they are precogs, with the Force able to start moving them out of harms way even before a trigger is pulled or a button pressed. Sorry for the double post.
Same goes for the master gunned down when order 66 is enacted.
Organic reactions obviously play a part on some level or no jedi would ever go down to gun fire because they can easily leap dozens of feet out of the way.
Oh it's always the dark side to blame isn't it, couldn't be incompetent leadership not with all those wise Jedi masters around.