some nice compositions in that set. looks like you may have been rushing or overly excited cos like ryan pointed out some of them are just out of focus. not sure what the deal is with the guys outfit for an engagement shoot....but anyway...i digress...

some suggestions...
take some deep breaths when you try it again, you need to be calm and make sure you are nailing focus. remind yourself every few frames to calm down and slow down. if its OOF the shots screwed so remember how important that is.
use your 70-300 as per above suggestion b4 you invest in anything else cos the first thing you;re gonna wanna do if you get even remotely serious is ditch that body.
use your flash some more !!