Possibly too much water.........or damage to the base of the shoots by molluscs.

Mine are the same and I put it down to too much pressure from heavy rain. Seems to happen to mine nearly every year if it rains heavily.

Nitrogen depletion, caused by the heavy rain, makes foliage lose its colour, though I'd expect other plants to be affected too.

Thannk you, I guess its the rain we have had, it has not affected the other poppies we have, they seem to be more like cactus than anything, they are just showing red. No idea how they got in the garden, but they are there and growing strongly.