[Bing]

mine are the same, I pulled them all up, peeled some and found little insects inside! however, some of the later planted ones are fine.

the bug looked like this one: allium leaf miner



or

[WulfrunFrank]

Just seen this tweet from the RHS. It seems that the weather conditions are the cause of the twisted leaf symptoms. The leaf miner is probably a separate problem occurring at the same time.

"Hail, wind, rain last month doomed some onions - many reported distorted, twisting & rotting - remove afflicted plants - only remedy"