nasturtium dullness

This year I grew Nasturtiums having grown them previously from seed. I sowed approx thirty plants which all came up.My question is, in recent days/past week or so, I noticed that some of my plants are appearing to look a little weak and near their end, as you’d see in Autumn. While they have flowered, and contain many buds to sprout, the leaves are becomming yellowish and droppy. Its particularly happening to my ones in the baskets and window boxes.My neighbour’s look similar, some of which are in the ground however. Of the ones showing these symptoms, the seeds have formed following the dead flowers. While some of the plants have aphids which you answered yesterday, and I did spray for, Im a little confused. Considering we are apparently in Summer, I thought these should last another month or more…The picture is of particular plant…ThanksDarren