The only creeping Grevilleas I know of are pretty much ground huggers and don't reach dimensions required to cover the side of a house.

Not sure but that leaf style can handle frosts. Similar leaf to fireworks / firecracker but no yellow with the red on the flower so it is not one of those two.

For a start I'd make sure the wood chips are away from the base of the trunk on both plants. Also, what sort of wood chips are they? Not sure but they could be your problem. By the way, I copied this from a comment on the plant: 'In order to maintain a healthy garden plant, the conditions must be suitable for propagation. G. rhyolitica requires a well-drained garden bed, with coarse, slightly acidic soil. Borers and scale insects are common pests to grevilleas and can cause considerable damage, leading to death if left unchecked. A minor effect of scale infestation is the growth of black sooty mould. This looks unsightly but is relatively harmless. In some regions of Australia Phytopthera and other diseases threaten both wild and cultivated populations. Most pests can be treated with commercial pesticides'.

While Australian natives are adapted to very low phosphorus soil conditions, only a minority of them are truly P-sensitive. Others don't need it, but can tolerate it in the soil, especially if the roots have adapted to those conditions (as opposed to sudden fertilization) and depending upon the availability of the phosphorous (some soils have higher fixation levels, making the nutrient less able to be taken up by plants). Protaceae is probably the most sensitive to phosphorous (Grevilleas are included here), as are many members of the Rutaceae family. It is also seen in some Mimoaceae and Fabaceae. I have had to fertilize some Australian plants, but it needs to be done carefully and with the correct ratios for the conditions and species. Although they don't tend to die with some deficiencies of Nitrogen, Potassium and micronutrients, their growth rate can be slowed. Plants that are being grown in areas where they are likely to experience P-toxicity often respond very well to supplements of chelated iron or iron sulphate.