Onion problems?

Since we have completely run out of vertical structures in our garden for our plants, I took the last two tomato plants (Marmande and Gardeners Delight) to the allotment and tied them into the frame covered in  pea netting. Whilst I was up there I inspected the onions. We have noticed that the tops on several of the onions grown from sets have died back and the roots have shrivelled up. Some have rotted around the base and others look like they may start rotting if left in the ground any longer. In an effort to try and salvage something from them I have pulled some of them up and brought them home. I'm not sure what has caused this since we have'nt had a lot of rain... not unless we have been too diligent with our watering! Most of the onions look ok, but vary in size quite a lot. Here are some of the larger ones:

The onions grown from seed are doing ok but are considerably smaller than the ones from sets. Apart from the onions I also harvested some fruit and an obligatory Little Gem lettuce:

The strawberry runners that dad gave me last autumn are just setting fruit, and the fruit are enormous! The handful of raspberries are from some canes that were on the plot when we inherited it. I am guessing they are summer fruiting? The gooseberries are also from a small bush that was also already on the plot. The variety of gooseberry is Hinnonmaki Yellow (the tag is still on the bush!) producing yellow/green fruit. I'm not very keen on gooseberries but will try and do something with them since I went to the trouble of picking them!