Maybe they want a good water as much as anything - or the leaves are just natural leaf loss. Give 'em a feed of something like Growmore, or Vitax Q4, unless your soil is neutral to alkaline, in which case, you can buy specialist acid feeds for these.

I gave mine a general feed plus a mulch of garden compost about a month ago

could be drying winds or sharp frost burn? have given all my acid lovers a dressing of sulphate of iron and general feed,they seem to be putting on new growth quite well,but my azalea hasn`t flowered this year, think bamboo may have a point about a good drink,it`s been a very dry winter again

Thanks everyone I shall give them a feed and keep them well watered. Thankfully we are not on a hose pipe ban at the moment but it has been quite cold at night also I get a lot of wind being directly under Manchester airport flight path. Thanks !!

Good news all my azalias are coming into flower and lots of new growth. I did feed them with liquid seaweed and have made sure they have had a good water daily as you all suggested. I think it might have been the dry wind and frost as you said.