How do you get a rose of sharon to grow faster?

I bought two blue satin and one pink satin I think last summer. They are about 2 feet high now so wonder how fast they grow and what can I feed them to grow faster?

Patience is often needed with shrubs--many of them follow the rule "first year they sleep, second year they creep, third year they leap", so it can be a couple years before they really take off and you see a lot of growth. You'll probably see some more growth this coming year (vs last year), but it's possible they may not really take off until the following year. Giving them extra fertilizer above and beyond what they need will do more harm than good, so I'd say as long as you're fertilizing them properly, giving them enough (but not too much) water, and have them in a nice sunny spot then you just need to hang in there and be patient with them.