IDP Roster Advice Needed

I drafted Brian Cushing, Tramon Williams, and Morgan Burnett for my starters.  Although we are only one week into the season, I can't help but noticed how poorly they all performed (minus - Cushing; give him benefit of the doubt due to low snap count).  Should I replace any of them with one of the following pickups which are available on waivers:  

LBs - Emmanuel Lamur, Brandon Marshall, Josh Mauga,  Joplo Bartu
S - D.J. Swearinger, Charles Woodson, Stevie Brown, Kam Chancellor, Tony Jefferson, Reggie Nelson, Tyrann Mathieu
CB - Antoine Cason, Johnathan Joseph, Bradley Roby, Brandon Boykin, Shareece Wright, Kareem Jackson  

I was thinking about dropping Cushing for Lamur and Burnett for Swearinger, but wanted to get an expert opinion before doing so.  Your thoughts?? What about CB... should I drop Tramon?

Scoring:
Tackles - 1 pt
Tackle Assist - 0.5
Sack - 3
Int - 3
FF - 1.5
FR - 1.5

Thanks in advance!

Burnett had 8 total tackles and led the team in that area, so wouldn't necessarily she he had a poor fantasy outing. That said, Swearinger is enticing as he is seeing a good amount of snaps as a nickel linebacker. I think their value is fairly close. Burnett is arguably the safer option as he has a historical track record of good fantasy performance but Swearinger has the higher ceiling. I'd stay put at CB.