Hibiscus is apparently tasty to many bugs and grubs and millipedes. Even mice, gophers, etc will eat them. With holes in the roots, not roots chewed off I would suspect an insect.

You can either pot it up, move it, or use a systemic that goes to the roots. I don't use pesticides so I would probably pot it till it recovers then consider moving it but you have to do what works for you.

If you repot, rince the roots off well to make sure any eggs are removed, if present.

Some people use hardware cloth to make a 'basket' around the roots of roses or hibiscus which will deter gophers, voles but won't help if its grubs, millipedes, etc.

Were they planted in an area that stays wet, or does it get watered every day? Hibiscus HATE wet feet. It sounds like root rot to me. It can leave holes in the roots as the roots die away.

Have you seen little brown moths fly up in your lawn? If so, you have grubs and they'll kill hibiscus in a heartbeat.

Have you maybe overfertilized it? People tend to want to fertilize sickly plants, but that's the worst thing you can do. An ailing plant can't take up the nutrients and the fertilizer will just burn the roots.

Most of the new fancy hybrids (like your Sunrise) aren't as hardy or resistant to pests and diseases as some of the older varieties. They're beautiful, but they usually don't live long in the ground.

I've saved a lot of different kinds of plants with this method, but if they are too far gone, it may not work.

(PLEASE all you experts, don't bash me and say this won't work. It has worked for me dozens of times. I don't give a rip what books say.)

First, if there are any green limbs, take cuttings and put them into water. By green, I mean if you can scrape a branch and see green. I'd stick to cuttings no more than 10-12 inches long. Put them inside in a sunny window, change the water every day, and soon you'll have roots and you can plant them in their own little pots.

Dig up the ones that are sickly, wash as much soil as possible off the roots and put them into a 5-gallon bucket of water with a whole bottle of peroxide poured into it. Let them soak for 24 hours. This not only kills disease, but the oxygen in it is said to be good for the roots.

Once they stop soaking, cut away as many completely dead roots as you can and sprinkle cinnamon on the rest of the roots. Cinnamon is great for killing fungus and bacteria. Plant them in brand new, sterile potting soil, and prune off 50% of the top. I know, sounds drastic, but the roots can't support the whole plant when they're rotted away. You may lose all your leaves, but if the plant lives, they'll all come back. It needs to use all its energy into making new roots.

Water well and after that, WATER SPARINGLY! Stick your finger down into the pot to your second knuckle and if it's dry, water it, but not a lot. You want the soil damp, not wet.

Good luck!