To get a diagnosis it will be necessary to send a sample to the plant disease clinic. https://pdc.umn.edu A microscope and sometimes culturing or growing up the fungus is required for identification. It may not be fungal. It is not possible to determine if it is from the photo. It does look suspicious however. If it is a fungus having an identification will make choosing the right fungicide easier. Picking all the leaves off is very drastic and will not get rid of a fungus it is probably on the branches, shoots, in the soil and on the pot.