Forgive me but I don't think many (if any) of the above suggestions meet shannorcal's criteria of 12-18 inches tall. Here's some short stuff: Achillea ÂMoonshine MOONSHINE YARROW Achillea x hybrids HYBRID YARROWS Aloe (many) ALOE Arctotis x hybrida VELDT DAISY Ballota pseudodictamnus BALLOTA MINT Dudleya pulverulenta CHALK LETTUCE Eriogonum crocatum SAFFRON BUCKWHEAT Eriogonum umbellatum RED-FLOWERED BUCKWHEAT Eriophyllum lanatum arachnoideum WOOLLY SUNFLOWER Erodium x variable CRANESBILL Eryngium amethystinum BLUE SEA HOLLY Euphorbia myrsinites BLUE EUPHORBIA Euphorbia rigida MEDITERRANEAN EUPHORBIA Euphorbia x martinii RED EUPHORBIA Gaillardia x grandiflora BLANKET FLOWER Geranium x cantabrigiense HARDY GERANIUMS Geranium x oxonianum HYBRID GERANIUMS Geum chiloense AVENS Helianthemum nummularium SUN ROSE Hemerocallis (dwarves) DAYLILIES Heuchera hybrids CORAL BELLS Heuchera micrantha ALUMROOT Lathyrus latifolius EVERLASTING PEA Mimulus aurantiacus hybrids SHRUBBY MONKEY FLOWER Nepeta racemosa ÂWalkerÂs Low CATMINT Oenothera caespitosa TUFTED EVENING PRIMROSE Origanum species and hybrids ORNAMENTAL OREGANOS Pyrethropsis hosmariense MOROCCAN DAISY Salvia chamaedryoides GERMANDER SAGE Santolina chamaecyparissus LAVENDER COTTON Santolina virens GREEN SANTOLINA Scabiosa columbariae PINCUSHION FLOWER Sisyrinchium bellum BLUE-EYED GRASS Sisyrinchium californicum GOLDEN-EYED GRASS Tanacetum ptarmiciflorum DUSTY MILLER Tulbaghia cominsii EVENING-SCENTED TULBAGHIA Verbena tenuisecta MOSS VERBENA Joe

Looks like scorch. Mine weren't too fond of the 100+ September temperatures either, and some scorching happened on mine. But these are too tough of plants, especially if that is Agapanthus africanus, to use the word dying. More likely than not, it will bounce right back. I don't know where you are located, but if it is in an inland/desert location, the plant may do better in a location with a bit of mid-day protection from the sun. I live in south OC, so there is an ocean influence, and my plants are mostly in half-day sun. But I see them thriving in full sun here also.

Oh, it is not easy to know whether this is an evergreen or deciduous agapanthus...but it has clearly flowered and is setting seed. I would actually stash the whole thing out of sight and ignore it. It is highly likely to be going through a transplant shock, given it's size and alacrity to flower, it probably thinks it is dying. There is really nothing you can do right now except hod fire and give it a chance to re-establish itself for next year. Allow the foliage to continue to die down as in any normal bulb, then store ot somewhere dry for the winter, watering just enough to keep a slight bit of moisture in the mix. If it is a deciduous type, it should come back as good as new next year (although it may be shy flowering) but if it is an evergreen, you will have to let the old foliage die off and allow it time to build up new leaves. Do you know the cultivar name...as evergreens would probably benefit from a shot of fertiliser, once the dying leaves have stabilised. You could also, at this stage, cut off the flower stems and tip the whole lot out of the pot and check the rhizome for rotting.

None of them look particularly like they are dying :-) A little stressed perhaps and maybe showing some signs of winter but mostly like they are not well suited to that location and the heavy rock mulch. That appears to be a very narrow planting area - how wide is it? What's the soil like underneath all that rock? Is drainage good? How much sun/shade does that area get? The first plant looks like agapanthus, the second clivia and the remaining ones strelitzia (although I am not certain - hopefully a local will correctly ID). I see nothing to be overly concerned about for the first two and the remaining three could just use a bit of a tidying. Any plant - even evergreen ones - will some periodic attention with regards to removing dead or damaged foliage, winter dieback (if any) and general grooming. But I would urge you consider the value and aesthetics of that overly narrow planting area and maybe enlarge and improve to a more plant-friendly setting or relocate the plants to a better location and remove the planter altogether,