How long have they been in the ground? Several years? Maybe they are crowded and need to be divided.

Yes, how long have they been in the ground? Was the 6" spacing for individual bulbs?

There might be more than one reason.

From the link below
2-Feeding has been with a high-nitrogen fertilizer. (This encourages production of leaves, but seems to quell the plantâÂÂs need for flowers.) Was the area fertilized?

10-Growing conditions the previous Spring may have been inhospitable -" the reformation of the bulb was affected. (An early heat wave may have shut down bulb rebuilding before it was complete.Lack of rain, coupled with an early summer can cause poor bloom the following season.

13-Bulbs may be out to get you! (The case when you give them away in frustration and they bloom wildly for the new recipient.)
How many years did they give you nice bloom?

What was the source of the bulbs?

Sue

Here is a link that might be useful: From the ADS site-Non-Blooming Daffodils

Thanks for your thoughts. They don't look crowded, don't get fertilized. We had a pretty good summer last year, a good balance of rain and temps. Individual bulbs were spaced at 6".