Rainfall probably inadequate. Amending of planting hole backfill undesirable, it affects how water moves into and out of planting holes so treated. Under dry conditions an unamended soil will often have a greater attraction for water than the coarser textured amended backfill, resulting in chronic dryness within the planting hole. For the same reason intact potting soil rootballs are apt to shed water to surrounding soil. You have to water so as to make up for this until newly planted stock roots into the unmodified soil beyond the potting soil rootball. If the planting hole backfill has been amended the plants may have to get into the unaltered soil beyond the planting hole before they are out of danger. Plants sufficiently damaged by poor moisture conditions within the amended planting hole may be slow to root out of it, or even die. Otherwise rooting into natural soil beyond planting hole often quick - within the first year after planting - after which top growth picks up nicely, creating the false impression that amending of the planting hole backfill produced a good result. Rocks cool the soil the same as organic mulch, it is the shading that is the main benefit as far as improving moisture conditions within the soil is concerned.

"cut worms" are not common issues with any woody plants. These are pests that attack seedlings primarily and at ground level (not below ground). I would be very skeptical of any cut worm creating this sort of rapid decline/fatal damage to an established pitt. There can be other organisms that can cause problems, however. A root knot nematode is thought to be responsible for widespread crop failures of pitts in southeastern climates but I am not sure how populous these creatures are in CA soils. I would be inclined to take/send a diseased/dead sample - roots and some soil intact - to your local extension office or plant pathology lab for diagnosis. If root knot nematodes are determined to be the problem, there are biocontrols available, including applications of beneficial nematodes. I would also not dismiss a root rot of some sort, as mentioned above. Pitts can be prone to a number of these pathogens and they are far more likely to cause that very rapid decline and death than just about any other issue.

Thanks. I haven't taken a plant sample to anyone yet, but I did send pics and info/questions to my local extension office who has responded by saying that the pitts look nutrient-deprived - likely further aggravated by excess water 'leeching' nutrients out of the sandy soil. Also, recommended I have soil tested for PH and nutrients. Never mentioned root rot, and said I might get new growth on them - but didn't say how. I typically put slow-release fertilizer on them twice a year, but this year forwent the fertilizer because of the way the were looking this spring. The thing that is blowing my mind about all of this is the fact nothing has really changed in the condition surrounding these pittosporums - like as in forever.

This is an outdoor shrub and I'm, not sure it's suited to indoor life. It's difficult to tell from the angle of the photo but the pot looks very small. And the poor thing looks absolutely parched, possibly beyond help. I'd take it to a bucket and immerse the whole pot and soil in water for several hours. Let it drain and cross your fingers.