I bought a couple of courgette plants to have a go at growing my own. The have started flowering and are growing courgettes now. i have 3-4 on the plants. they courgettes look great neat the stalk of the plant but as you go down the length it gets thinner and don't look very healthy. a bit yellow. Any idea what I am doing wrong?

'Fruits swelling only at the top, often with shrivelling and rotting, indicates incomplete pollination, usually due to cold temperatures. The problem should decrease as the season progresses. '

Could this be the problem?

could be. It hasn't been very warm here. thanks