..."Wart-like spots unrelated to pests"... could be oedema. If scale, it is regular, more or less oval in shape. It could be scraped off by fingernail or swiped off with a cotton ball or q-tip moistened in rubbing alcohol (that will kill it on contact). No extra pressure is needed. If you try to scrape off oedema bumps, it will leave a hole in the leaves. To scrape it off, more pressure is needed. Also, spots can be round and raised, like a hard pimple, or much more irregular in shape, and more flat. Leaves with oedema shouldn't be removed. It is physiological disorder, not a disease. Improving cultural conditions should help.

Scale insects are like barnacles on plants. The juveniles can crawl and then they settle in and stick to one spot. They can be scraped off but are fairly impervious to insecticides unless they are applied when the juveniles are not yet anchored in place.

I only used rubbing alcohol, and it always worked. Just make sure it gets right on the bug. I wouldn't bother scraping them off - it is gross to me - suggested it only as a test to find out if bug or not. I prefer q-tip as described...But op has no bugs here.