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Rose of sharon is not a thorny plant, so the plant that is growing is not a rose a sharon.

In my experience, the Rose of Sharon shrubs are one of the last to leaf out in the Spring. My Forsythia bush has even been very slow this year for some reason. So I would give them a good full month yet and see what happens. You can certainly give them some water with root stimulator and a product called Super Thrive mixed into the water, this will help give the root system a little wake up call and help it get going so the top growth comes on well. Here is a link to an article of interest for you too: https://www.gardeningknowhow.com/ornamental/shrubs/rose-of-sharon/pruning-rose-of-sharon.htm

Rose of Sharons typically don't leaf out until early summer. Here is a close-up photo of a rose of sharon's foliage to aid in your identification once it does start leafing out:

http://www.hiltonpond.org/images/RoseOfSharonLeaf01.jpg

If the leaf doesn't match, then would you be able to share a photo with us? It would aid in our identification of your shrub.

For more information on rose of sharon, please visit the following article:

https://www.gardeningknowhow.com/ornamental/shrubs/rose-of-sharon/rose-of-sharon-bush.htm

This article should help: https://www.gardeningknowhow.com/ornamental/trees/tgen/tree-leafing-problems.htm

I would prune them down too and see what happens. You might try mixing some Super Thrive and Root Stimulator together in a two gallon watering can full of water and give each of them the full two gallons of the mix. Do that 3 or 4 times when watering is needed, if that does not get them started, well, they are likely totally gone.... :-(

Once the main tap root has been removed, the other roots will naturally decompose back into the soil. Adding a high nitrogen fertilizer, chemical or organic, will help speed the decomposition of those roots.