I'd collect some in a clear glass jar and visit your local Extension office. Your image isn't macro enough to differentiate between the usual white soil crawly things.

Could be (to my eyes) symphylids, springtail nymphs, termite larvae, for example.

what she said as to ID ...

i like your theory of a population explosion.. if your mulch is new ... a lot of organics.. will attract things that use such ...

regardless ... you give no indication of any problem with any plant ... and as such ... there is no requisite remedy ... i dont worry about soil creatures ... they are usually.. improving the soil ...

but the ID ... will help make that determination ...

ken

Collect a few in either a clear glass jar with a tight fitting lid or a sealable plastic bag and take to your county office of the University of California Cooperative Extension Service.

The browning of the tops of that Liriope may be scorch,
http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/environmental/scorch.aspx

Here is a link that might be useful: University of California CES