You don't need to store it. In fact, you cannot store feed for long periods without depleting its nutritional value so just go ahead and feed it to them, even if you mix it with the Flock Raiser. I feed my birds Tucker Milling mini layer pellets which are 16% protein, but they contain good porcine animal protein, unlike many feeds today. The trend toward vegetarian feeds led to feather picking and other issues and wasn't a natural feed, especially with penned flocks without access to good green forage and lots of bugs, lizards, etc. Tucker Milling also makes a 22% layer pellet, which I sometimes use in a period if I have numerous heavily molting hens at one time.
And all layer feeds are non medicated, for good reason. If there is a medicated layer feed, I sure don't know about it nor would I ever feed it to mine.