Picture posting is enabled for all :)
I thought mg deficiency was more spotted yellow patches. Perhaps it is nitrogen deficiency. They are hungry plants. Give them a feed. The older leaves do start to yellow off anyway.
I'm in essex, my pumpkins are now all orange and the leaves have all dropped off and died back.Could be the variety, could be the climate we've got down here. Even sweetcorn is almost ready and the beans are just finishing. Can't remember when I planted, think I blogged about it on my blog www.waark.com but don't have time to check now (just thought I'd add my 2c)