Or they may have become overcrowded. If this seems likely dig up the bulbs, separate them and replant.
Mulch....in fact...all 3. Dig 'em up in a few weeks when the tops turn brown & crispy. Replant them spaced-out (the bulbs - not you) a couple of inches apart about the same depth you found them at. They need a location with full sun in the Spring; doesn't matter if the deciduous trees shade the site after their leaves come out. This fall add a nice layer of a couple of inches of mulch or compost. Next February when the bulbs poke their noses up, fertilize with a low-nitrogen fertilizer suitable for bulbs (if you want to be organic, substitute well-rotted manure) Then, if you are like me, you can ignore them for a few years till they get hungry & crowded again.
I got best response from lawn fertilizer, this brought back a grouping that was being diminished by narcissus bulb fly. Typically on gardened soils in this region it is nitrogen that becomes deficient, with phosphorus and potassium often being adequate - away from heavily leached parts of the outer coast. In addition, many products sold and used are high in phosphorus and may produce a toxicity when used repeatedly. A landscape architect I talked to yesterday related how diverse kinds of plants installed together on an imported soil used for a residential project all produced the same discolored growth afterward. A soil test showed that the phosphorus content of the soil used was off the chart.
Thanks for reminding me once again, Ron. I use mainly manure & compost supplemented with manure these days & tend to forget about nitrogen leaching. The organic matter seems to hold nutrients better & in a decent balance to me.
