Do you use
PoolMath app? There is a bleach calculator that standardizes the cost with varying % concentration.
So 12.5% at $9.40 is $0.588/oz and 10% at $5.47 is $0.427/oz. So WalMart is clearly cheaper.
You may want to run your FC at the high end of the range for your specific CYA. This will help offset the effects of the flowers falling in the pool. My guess you are running on the minimum FC requirements and anything additional such as the flowers will cause algae to grow. Please Review the chart for levels using liquid chlorine.
FC/CYA Levels