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Pittosporum can drop leaves at times; especially during times of stress. Try morning sun and afternoon shade. Keep the container moist but never soggy or dried out completely.
Soggy roots can cause root rot quickly with Pittosporum.

Pictures loaded wrong...T clarify-photo 1 shows both old and new plant side by side (new plant is smaller one on left). Photo 2 shows new plant leaves closer up. Photo 3 shows old plant leaves close up.

Though I am not completely familiar with the pests in your area, I would be likely to say that it could be an animal that is damaging them. If possible try and enclose the area in fencing, or even wrap the trunks very lightly individually.

Here is an article for more information on the plant: https://www.gardeningknowhow.com/ornamental/shrubs/pittosporum/growing-japanese-pittosporum.htm

Make sure that you cut this compost with potting soil, or it could be way too "hot" for the shrub. This would explain the burning, or dropping of leaves.

The next concern would be how much drainage the container has, and how much water was used. This could also be symptoms of a fungal infection, which can happen when soil remains saturated for too long, or sits in excess water.

I also recommend dolomitic lime added to the soil to keep the pH stable. Wettable sulfur will kill off any harmful microbes, as well as keep the soil conditioned to prevent bad infections.

It is impossible to dianose and make recommendations without knowing more about the growing conditions and your soil and water management. Neem oil is not a cure-all and in some cases it is not appropriate treatment. Wrong dilution rate can cause burning of foliage.
Look first to water management, too much or too little? Too little is most common in cases of decline and die-back. If the plants have adequate irrigation, then consider fertilization and mulch. There are insect pests to consider.
Here is link to artiles on Pittosporum growing tips.
https://www.gardeningknowhow.com/ornamental/shrubs/pittosporum

Was this actual mineral oil, or was this a home meade soap oil? Actual white oil will not cause these symptoms, but soap can if it is not diluted enough.

Another issue could be that an insect is not to blame for the damage. Fungal issues are very common and can look like scale sometimes. Insecticides will not be effective against infections of this nature.

Can you include a photo? This will help me to see what is going on, exactly. Then I can recommend the best remedy from that point.