About 2 years go, in the autumn, I planted lots of daffodil bulbs. The following spring, the bulbs flowered. However last spring, although there were green leaves, there was no flower. It looks like the same thing will happen this year as I can't see any buds. Do I need to dig the bulbs up and plant them deeper or were they a duff bunch of bulbs and need digging out and chucking away? How can I prevent this happening in the future?