Sounds like lack of water to me, possibly coupled with to much sunshine - they need semi-shade.

Thanks! THey are in full sun from about Midday and it can get preetty hot here. Will see if watering more works..
Should I feed them now or is it too late? Any suggestions to help them come back a bit.. they look pretty sad!

You will have to move them if they're in full sun from midday onwards, far too hot for them, they only like dappled sunshine, such as comes through tree canopy overhead.

And.. what sort of compost do you have them in they need acidic soil. Glad you joined GoY Nugent so we could talk. Where are you in France, rhododendrons really like coolish, damp condition - think the himalayas!