'Gold' Sage Growing Slowly

We bought a golden sage plant (I think it's "golden" v "gold"; there was no stake and it was long ago) from you in May. It is still alive but has grown very little if at all since planting. It seems healthy enough, just small.
It is near, but not shaded by, a purple sage bought from you at the same time and a regular sage bought locally a year before. Both of those are more than thriving! Good soil, ample water, full sun, etc.
Are we doing something wrong, or will it improve in its second year?

I am assuming that you have the 'Gold' sage cultivar we introduced in 1999. This cultivar is a slower growing variety compared to others such as the standard garden sage and the coloured leaf cultivars 'Tricolor', 'Purple', and 'Aurea' (also known as 'Golden').
'Gold' is a naturally slow grower probably because the leaves contain fewer chloroplasts, the organelles in the leaves that contain the green chlorophyll. With less chlorophyll, the plants photosynthesize at a lower rate than other sages. Photosynthesis is what drives growth.
As with other sages, 'Gold' prefers a well-drained soil of moderate nutrient richness. It does not tolerate wet or soggy soil very well. It also requires full sun to keep photosynthesis at a peak. Overwatering or overfertilizing, or underwatering during drought, can cause sage to grow slowly. With an already slow-growing plant such as 'Gold' sage these effects can be more pronounced.
Provided the soil and sun exposure conditions are adequate, the plant should start to show some new growth before the summer is over. It is important to protect the plant over winter with mulch if you are planning to leave out. Next season it should begin to show more growth.