Possibly a deficiency....magnesium would be one guess

I thought the top one was a leucothoe also but as I don't grow and not familiar with Sarcococcoa I wouldn't take my word for it.
Leucothoe require acid condition and both would prefer a shady spot. I found that Leucothoe struggled in a south facing bed in my garden, it wasn't happy. I moved it to a spot where it got plenty of shade and it has thrived.

Definitely both are leucothoe. Neither looks in poor nick, in fact, L. 'Scarletta' is meant to go that sort of colour, but I suspect yours has had too much sun (should be a darker red!). The top picture is probably a leucothoe fontanesiana cultivar, and that leaf colour is perfectly normal on older leaves, but especially if the plant is stressed through drought or too much sun. As Scottish says, they're happiest in shade, and like a lot of those plants, prefer a neutral to acid soil.

Poor sunburned babies. The Sarcococca will need shade, and can cope with full shade in either dry or moist soil. So if you have a grotty corner anywhere, I'd rehome it to there. I'd personally leave the Leucothoe and wait to see, as it does alright for me southfacing in a mixed border as long as the surrounding plants give it a bit of overhead cover in midsummer. But again, if a grotty corner needs filling...

I also think they are both Leucothoe. Sarcococca looks totally different.
my Leucothoe are also turning into their autumn colours now. Certainly the top one looks as if it needs a dose of salts [magnesium sulphate or cheaper as Epsom salts from the chemists].