Disaster sriking my pelargoniums!

Benarch

i have managed to keep these plants for about 5 years and they have thrived. However over the last 3/4 weeks they have been literally falling apart. Yellow leaves followed by stems breaking off! I wondered if i had over watered so let them dry off thoroughly before watering again. But to no avail. Could it be vine weevil, but would they attack all 6 plants?
 The pictures i have posted show the plants where i have removed the dead leaves hence the reason they look so sparse!

Buttercupdays

They look thirsty and starved to me!

In a hot spot like that with lots of reflected heat they will need more water than in cooler places and they also look desperately in need of repotting - into some decent compost.

I use John Innes No.3 with about a third multipurpose for mine and they do appreciate an occasional feed when in full flower.

I would water, wait for them to recover a little, then repot. Hold the feed till next year, as they will slow down as winter approaches.

Dovefromabove

I agree ... pelargonium leaves redden when the plants are stressed, usually by drought and/or starvation.