I'm tempted to say mildew for the brown spots - spray with Roseclear.
Yellow leaves - no idea but what an unusual effect! Yellowing leaves are usually down to too wet/too dry/too alkali but generally looks more like the whole plant is 'off colour' rather than that striking yellow.
If no-one comes up with a suggestion you could try sending the image to the RHS or one of the specialist rhododendron growers.

Will the RHS answer questions from non members?

Many rhododendrons have a brown furry layer on the underside of the leaves - the indumentum. It's normal.
The yellow colouring could be a nutrient deficiency, what type of soil is it growing in?

pH 6.5, not brilliant but I planted it in ericaceous compost and did given it ericaceous feed last year. It had its first flower last year but none this - thought that might be because of the long dry spell though. The ponticum flourishes in similar ground, but it would, wouldn't it... never spreads around though.

I wouldn't worry too much about the yellowing of the stems as this can often be natural in the development of some varieties of rhododendrons. If it had been the whole leaves that had turned yellow then yes, a feed of iron or magnesium should do the trick. As far as the leaf spot is concerned, then as already advised a fungicide would sort it out. But just as the same spotting is quite common on Red Robbin, it will most probably return. If the plant still continues to thrive, then I would leave well alone.

The leaf rolling bothered me as much as the yellow stems Jimmy - I don't think that's normal?

Rhodos curl their leaves if they become too dry or the ground is frozen for a considerable period of time and they can't access any water. The yellowing would indicate to me that the Rhodo needs feeding with a liquid ericaceous feed, though as Jimmy says with some species Rhodos it is normal. If the spotting on the leaves is on the Ponticum I wouldn't even bother spraying it takes a heck of a lot to kill that particular Rhodo.

The RHS won't answer questions from non-members, but check out the info on their website.

Do you know the name of your Rhodo Stera some are grown primarily for their foliage and produce few, if any flowers, we have one we grow simply for its indumentum.

A pH of 6.5 is very high for a Rhodo to grow in, you may need to have in a large container.

Maybe the RHS won't answer questions from non-members online, but if you can visit an RHS garden, you can simply take a sample to their enquiry desk. (I'm not a member but did this once at Wisley). Also, a good nursery should be able to advise you - best of luck!

I'm a terrible label loser MG! The large ponticum , a mature azalea (in its third home!) and a Pieris seem to do ok with the occasional iron boost. I wanted it in that position rather than for its own sake so I'll struggle on with it where it is for another season with appropriate feeding as suggested and see what happens. It did have a lovely flower last year for the first time. I bought it on the recommendation of the nursery for where it is, & I must have mentioned the pH then because I knew it was iffy.

Re the leaf curling maybe it happened in the dry spelllast summer.

Shelia, how lovely it would be to live within reach of an RHS garden! I could always ask the nursery I got it from.

So thank you very much everyone for your very helpful and encouraging answers. I'm not quite convinced that the fuzzines on the back of the leaf is natural but am keeping my fingers crossed for now that Landgirl has the answer to that one!

Just a footnote - Ericaceous feed helped the yellowing, leaf curl disappeared and full of gorgeous flowers this summer - happy days!

Hurray! Thanks for the update, Sue.

Good to know!

:)
S