How long have they been in the pots, Love3garden? Do you water them with collected rainwater only if you live in a hard water area? Have you repotted them and not used ericaceous compost? I think these are all areas that could make azaleas unhappy.

I have one too, Love3garden, and it's quite healthy so i think it might be to do with the conditions you have for it there.

I have mine in a 14" diameter pot that's about the same depth, it's in ericaceous compost and in a position that's shaded for most of the day.

It only drops occasional leaves and it's when it gets too dry but with yours turning a yellow colour i would think that it's chlorotic and the soil perhaps need changing - potted plants need their soils/compost changed every year or so as the nutrients get used up but this family of plants need specific ericaceous soil.
So, is the soil ericaceous ?
Is in a shaded position ?
is it watered enough ?

I changed the soil and potted it up in late summer. I have always used ericaceous soil.

I live in yorkshire which is generally a hard water area and have to admit have been using tap water out of laziness as i do not have a water butt, but collect water in a large bucket which i've neglected to do over the last few months. The soil does tend to get very dry by the time i come to watering them as they are in a full sun position which may be the culprit as i have 2 other azaleas in a partially shaded position and they are doing fine.

If i move them to a shaded area and start wetering with rainwater, will they recover and flower next spring?

As you say it's only some of the leaves that have gone yellow and fallen off, I'd say go for it L3G. Move them into more shade and be careful what you water them with and I expect they'll pull through. *crosses fingers* :-)

Thanks for your help guys, hoping for a beautiful display this spring :)

I'll just add that i water mine with tap water and we've quite hard water here, so i'd say it was most likely to be the full sun aspect it dislikes and combine that with the soil drying out - these are both situations are the opposite of its natural habitat.

That makes sense Louise as the other two azaleas are doing fine with tap water. So it probably is to do with them drying out in full sun in their terracotta pots. Its easy to neglect watering at this time of year as it pretty wet here, but the pots are against a wall and the foilage on the plant prevents the soil getting a good soak. I have moved them now to a more shaded area and will defo water them more.