Give the impatiens a dose of fertilizer. dilute the fertilizer to 1/4 strength according to lable and make sure the basket is not allowed to dry out. You can also pinch back any long stems. They should reflower in 2-3 weeks.

From now on, fertilize every 2-3 weeks with a diluted fertilizer.

e.g. if you use Miracle Grow 15-30-15 then add 1/2 tsp per gallon of water every two weeks. If you use Peters 20-20-20 then use 1/3 tsp at same frequency.

You will need to water more frequently, but just use the fertilizer every 2 weeks.