This is a mix of extreme scarring after scale and neglect + secondary fungal infections. Scale insects are constantly opening entry doors for pathogens and there's plenty of fungal spots and scars that are a direct result of the scale infestation on the plants. Imo you should probably improve the conditions before you do anything else. More sun, quality fertilizer, mineral soil, regular weeding etc. These kinds of problems are directly connected to poor environmental conditions. Scale is a problem, but healthy plants should be able to suppress them.