I bought potassium pills at the Dollar General store for my husband s leg cramps. They are made by Rexall Naturalist. He is afraid to take them because they are from the Dollar General strode. They are potassium chloride, potassium gluconate, potassium citrate, potassium nitrate, potassium bicarbonate,potassium sulfate. 99mg 3% daily value. Are they safe?