Sorry to say, it's almost impossible to grow anything directly under any kind of pine. In fact, I'm surprised your hostas survived at all. You could try some tough ground covers such as epimedium and vinca, but I really think that the list of plants that will survive is very short. Or, you could try putting some shade-loving annuals in pots and grow them under the trees. Containerized plants will have a bit better luck because they won't have to compete with the roots of the pine trees.