Rip out as much of the K31 as practical then heavily overseed with Rebel Supreme. Apply a STARTER fertilizer at the same time. This is an ideal time of year to do this.
You may need to find out the best grass for your area. Many homeowners in my area (east TN) use K31. Rebel Supreme is the best grass seed for my area, but the best may be different for your area. The reason most people buy K31 is that the cost is less than Rebel Supreme. I'm too far south (hot summer droughts) for Kentucky bluegrass, my favorite. Whatever you do now, the effect won't be seen until next spring.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.