If they're dying that quickly, you're probably getting crap bait from the bait shop. Or, if they're fine out on the lake and dying when you get them home, you might be shocking them. If you transfer them to different containger or change the water, make sure the water is the same temperature. I usually keep a 5 gallon bucket full of water next to my minnow cooler, that way they're the same temp when I go to change the water, and the chlorine evaporates as well.