Welcome to the board creekscout.

First off, you need to be sure that the growth of the alfarack did not do well because of the drought, or because of other factors. For instance, if the soil is below 6.0 Ph, it wouldn' t matter how much rain you got, the alfalfa mix would do poorly, an grasses would flourish. If you did a soil sample, and applied lime at, or just prior to planting, enough time has not likely passed to allow the lime to have much effect - it can take 4-6 months.

As far as applying poast and/or roundup - you need to be sure you are getting active growth for them to work. Most people would suggest mowing any growth over 8-10" , waiting two weeks, while new growth starts - then spray. The sprays can work in a couple of days with daytime temps in the 70s. They may take 2-3 weeks to work properly in 50-60 degree temps, as growth is slowed, as is the uptake of the chemical.

Good luck -