They should do just fine. Yes to fertilizing them now. But go lightly so as not to burn the foliage. The foliage should grow for a little longer then die off. Dormant period is in the summer for daffs. So a shot of half strength soluble fert might be just the ticket.
The healthy foliage makes the new bulbs you will plant in the fall. The more good foliage you have the nicer the bulbs will be. But don't be concerned when the foliage dies off gradually in a month or two. (depending how quickly the weather gets hot) The bulbs make new roots over the winter before they start putting up leaves. I have never fertilized them in the fall, but some people like adding bonemeal into the planting holes. Daffs naturalize, return and multiply with no help if they like the location you give them.I like to plant them under deciduous trees so that the blooms last a bit longer. In full sun they are so fleeting.
Also, don't water too heavily over the summer, the bulbs could rot if they are kept too wet. Maybe set the pots where they will just get whatever rain falls, not where your sprinklers will water heavily. If you have a long hot spell with no rain you may want to water them lightly.
