Why isn't my red chokeberry leafing out?

canishel(z7 TN)

I have four aronia arbutifolia shrubs planted in various places: sun, part shade, pot. All have the beginnings of leaves, but none have fully leafed out. They have looked like that for over a month. Meanwhile, the aronia melanocarpa are fully leafed out.

What's the problem? Why is the red different from the black in growth? I'm in zone 6b.

Thanks for any help.

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