Well I went to the RHS today and asked them what they thought was affecting the sunflowers and, in their opinion, it's something in the soil. My sunflowers are in a raised bed which I topped up in April with a planting loam supplied from a local company who I have used lots of times in the past with no issues. Also i have courgettes and sweetcorn in the same bed and they are fine. But the sunflower seeds I have planted elsewhere in the garden aren't affected in the same way so maybe it is something in that soil. Anyway the advice was to feed them with a nitrogen rich feed and not to let them get too dry. The adviser thought that the plants and flowers may be stunted. 🙁
My sunflowers have come into flower and are looking lovely in spite of their dodgy leaves at the outset. Photo attached. Hope all of yours came out ok too!
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