You should collect more reds and yellows to get BN/SR.
I try to, and I've gotten a little better at it.
You should practice saving reds and yellows by placing them on either the left or right lanes. You should place reds and yellows in the center lane only when you're ready to match. If you place reds and yellows in the center lane early your matches of reds and yellows will be smaller than you want them to be. Placing reds and yellows on the left or center lanes is the concept of priming with pointman.
Usually I'll stack one or two of the first main color in both corners, then one or so of the second main color until I find a good moment where I can drop many of the first main color into the middle starting the match, then I try to build the middle up and over the second main color on the sides, while maybe dropping a couple more of the second main color if I need to to extend the match, then I try to keep room for a three block match of whatever non-main color I can pick up for the sync bonus. Then after that match clears, the second main color blocks fall and start another match, and so I try to alternate like that.
I do tend to mess up a lot with the faster tracks like this one, and waste too many main color blocks in small, isolated, unconnected matches. I have a problem of holding the scoop down constantly, not being able to let go and instantly place a block or group of blocks when I should, which can quickly catch up to you, overfill your queue, and mess up your board on the faster tracks.