hi everlasting,
Speaking only from my own experience, LBS really likes sharp drainage to do well...I have some clumps growing at the edge of my cactus bed in slightly elevated pure gravel (right out of the pit, so it's a mix of coarse sand and small pebbles) never watered except by rain, and it's easily the healthiest planting I have of it. I've tried it in heavier soil and it just doesn't do very well at all, and I'd suspect it hates getting wet in such conditions.

I dug up some clumps of Little bluestem & transplanted them this spring to an island in the middle of the cul de sac. I watered them well when I put them in, but then I forgot about them. They have turned yellow & died. I suspect that your new plant plugs need a little coddling this year, maybe some mulch & extra water. If they survive, then they won't need mulch or extra water next year. If they don't make it, try planting seeds instead next year. It may take a bit longer to get a nice size clump, but it is actually easier to start them that way than from transplants.

I suspect too little water is the problem. It isn't easy to overwater in most outdoor situations. If you have an automatic irrigation system in place and you are watering daily, then too much water might be the problem. Otherwise, too little is probably the problem. Although these grasses will be very drought tolerant once established, right now they have very limited root systems and cannot cope with dry soil the way the will in the future.