They look like they came from the discard rack at the Big Box, pre-dried and half dead. A Miscanthus should not look like that. Some other grasses and sedges can look like that. On purpose. You don't want a grass that big, Miscanthus average size is 6' wide x 8' high, in such a tiny space so close to other plants anyway.

What should I do

I'd remove them and call it a learning experience. Planting anything when temps are in the 90s is not going to go well.

They are a little heat frazzled, that is all :-) Transplant shock. Nothing at all wrong with them that time, adequate water and another growing season can't fix.

I do agree that may be too many in too small a space. But like many plants, different cultivars of Miscanthus sinensis come in a wide range of sizes, including some that never exceed around 3" in height and a similarly more compact spread. But without knowing what cultivar you planted, would guess you might have overplanted :-) But you can safely wait until next spring to relocate. They certainly won't get overly or unmanageably large between now and then!