First off, I'd drop Bryant for another kicker. Having Julio out hurts ATL's offense, that's already struggling a lot. He already hasn't been nearly as goo this year, and I'm not sure it's getting any better. Succop from KC has been doing really solid, and with KC's ability to move the ball, and not put it in the paint, could be a good every week option. Also, your boy Sturgis from MIA has been doing work, take a look at those two.
Regarding Blackmon, I get it, everyone had high hopes for him, and for the majority of last season he was extremely mediocre. But his last 5 or 6 games last year, he was a top 10 wideout, and he picked up right where he left off putting up 140 and a td last week. His coach has said he's super stocked with him, and I'm feeling pretty good about him. Hopefully I'm right, but go with what you feel homie.
It looks like you grabbed Allen already, good move. With Floyd out, he could very well emerge as the #1 option in SD.
If you're not in a 2 qb league, there's not a whole lot of reasons to roster 3 of them. Brady will turn it around, especially with getting the Gronk back. Honestly, I would consider combining maybe Rivers and Hilton coming off a huge game, and see if you can get a top 10 wideout or a solid RB in return. Something to think about.