I'm sick

Looks almost like a deficiency. You could do as grindle says or try feeding it with sequestered iron (Sequestrion of iron). Mulching with ericaceous compost or rotted pine needles is also good to keep the ph low. Though not true ericaceous plants, they like similar ph levels.

Well it's chlorotic so you need to sort out the soil and the nutrients and is it in full sun there ?? If not it needs it, they love the sun and the warmth.
It also looks a bit too cramped there alongside the other plants, i'd be inclined to give it its own space and in the right soil and right orientation it'll buck right up.

I'd use Sequestrene Merlin, and ensure that the entire bed is ericaceous or move it to it's own space.
I'd also make sure it doesn't dry out - but doesn't get too wet feet - the fact that the Sedum is thriving there indicates that it's a very sharply drained area and that's probably too sharp for the Gardenia.