I doubt you're doing anything wrong. A period of local climactic adjustment is expected.
Red coloring on any Yucca I've ever owned indicated stress, usually water not getting to the whole root structure. What your situation is remains unknown.
Red is evident even in the last photo although somewhat less pronounced.

Cheers, Barrie.

Barrie,
Thanks for commenting on what could be wrong.
I will increase watering a bit, especially now that it's hot again.
Barb

They were likely grown in a greenhouse. The greenhouse filters out sun light and has less quick changes in the climate. Therefore, the plants aren't acclimated to withstand the more harsh conditions outside. Just wait and they'll be fine.

turtile, hadn't considered that; excellent point.

I'll move them out of the hot all-day sun.
Thanks.
Barb

Barb,
Do you have any updated pics of these yuccas? 🙂

Hi Aaron,

I did a bit of an experiment with these 6 y.rostrata after receiving them last year.
Wanted to see how they'd grow in various size containers.

This pic is of one I left in its first 10" tall container, increasing watering a bit as suggested.

The next pic shows two, each in its own 2 gallon pot....thirsty day! 😆

The next pic is of three that I planted in a big clay urn, with fairly good soil. The 2-headed yucca is in foreground. It looks different than the rest in its color, so I doubt it's a rostrata.

What I learned is that soil type isn't important, but that roots need more space than I had thought.

Result: if not planting these y.rostrata "sapphire skies" in the ground, give them a big pot, at least 2 gallon.

The y.rostrata in poor soil did the same as those in good soil, but the individual plants in 2 gallon pots did best, and look the healthiest, despite being in so-so soil.

And here's the pic when they arrived July 2008:

I wasn't sure of what fertilizer to give, so they've basically had very little of anything but water.
All were protected in the cold building over winter.
Barb