It's probably transplant shock. Even with abundant rain, newly installed plants have trouble taking in water unless their rootballs are soaked every day. They've been happily living in a greenhouse, being watered at least daily, and now are trying to make better root systems to cope with living on their own.

I sure hope so! Would hate to lose $100 worth of plants. I don't really have the money to replace them this year if they don't come around. How long before I should see an improvement?

The browned tips will last until you cut the plants back next spring, but the plants should be ok. If some blades die back more than half, you can cut off the brown. Cut them at an angle, because some of them will continue to grow in length, but will have whatever shape end you leave on them.

Pennisetum 'Rubrum' is hardy in OK?

No, not unless we have a mild winter. But I like it, and wasn't having any luck finding the Pennisetum species so I bought these in the mean time. Most likely they will be replaced with the species or Hameln next year

Just curious. I can't grow it here and you are colder than me.

I grow it as an annual. Our summer is just hot enough, and fall stays warm due to the influence of the bay. I get good height and good blooms, and as long as I can get them cheaply, it's worth the expense.