Yes, they are heavy feeders, a well balanced fertilizer is a good way to go for most plants, it takes the mystery out of fertilizing, I use a 16-16-16 mid March for all my plants.
Thanks. They do get a lot of sun, most of the day. And I didn't think they were planted deep, they were put in at the same level as soil. Anything else I can do? Do I need to feed them?