I believe this is Chamaesyce vallis-mortae. Note tomentose leaves, inflorescence generally clustered at branch tips, and (at least) one cyathium with a yellow-green involucral gland (as mentioned in the terminal key couplet for the taxon)...though most are red-dish. [A speculation: Perhaps some involucral glands begin yellow-green and become red-dish with age?]

Further support for C. vallis-mortae here: Only two species of Chamaesyce appear in the carefully researched 2008 ''Vascular Flora of the Owens Peak Eastern Watershed, southern Sierra Nevada, California'' by Naomi Fraga (available as a PDF here). Those two species are C. albomarginata, which is glabrous...and C. vallis-mortae which is tomentose, like the plant here. Also, a number of UCJEPS voucher images look like a good match, for instance this one.