[m1ckz]

my and others on allotment have there onion top leaves going brown   any idea what this is  mine are quite big so ive pulled then out an left to dry  cheers

[mumofstig]

Lots here have gone down with mildew again, perhaps you've got the start of that - and saved them in time.

[Salmo]

Probably bruising from the recent winds. If they are winter onions they are probably thinking about finishing anyway.

If they are Spring planted then give them some water, perhaps with high potash liquid feed such as Tomorite.