"Glenda" wrote
Last year my fritillaria imperialis all came up with flowers on them
and looked great. This year, only a yellow one was flowered. Another
has shot up but has no flowers on it while some of the others haven't
grown to full size yet. I have been looking for red lily beetles on
the plants but can't find anything, is there another pest that would
have caused damage to prevent them from flowering and growing
properly?

Yes, Red Lily Beetle last year eating the foliage and stopping the bulbs
taking in nutrients.

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Regards
Bob
In Runnymede, 17 miles West of London