sea holly wilt

Please don't think that @thriftybri. We have all been stumped one way or another by unidentifiable plants. With you mentioning 'blue stem' in your original post I immediately thought of the spikey leaved variety. As @Puncdoc stated, there is a smooth leaved type but that does tend to be more green than blue. They are tough and do need to be outside and fingers crossed your remaining 3 flourish.

 

blue on picture on the box

 

Don't feel like an idiot, if it's not a Sea Holly it's nothing you've done. If it came out of a box labelled Sea Holly it's what you expect to grow.

 

Apologies @Punkdoc, I misspelt your name in a later response to the original poster.

 

Sea Holly seems to be a common name for eryngiums and it does look like a young eryngium plan um, which are quite commonly found bare root.

I think it's to warm and wet, they tend to like good drainage and are very drought tolerant because of their deep fleshy taproot. I would follow the advice above and slowly acclimate them to outside conditions.