I agree that it LOOKS like mechanical injury, but if it leads to the eventual loss of the entire leaf, we need to look to other possible causes. If that (in the picture) was evidence of mechanical injury, we wouldn't expect it to spread to involve the entire leaf. What has your nutritional supplementation program been like? Do the lesions appear to be prevalent on either new or older foliage? Al

Actually that looks to be a philodendron brandtianum. or Philodendron Brandi more commonly. It doesn/t have the hook shape of a scindapsus, satiny texture or silver edge around the leaf (Silver Splash doesn't have the silver edging, but the other 4 varieties all do). I had a similar issue start on mine and it was from the tap water I was using to water it. I started using fish tank chlorine removing drops and letting my gallons of water sit for 24-48 hours and it went away.

Possible webbing on the back of some leaves and stippling of the center-of-attention leaf in the bottom pic are evidence toward spider mites. Wiping the front & back of leaves with a cotton ball damp with rubbing alcohol can help get rid of them if so, and clean leaves if they are not even there. Does this pot have a drain hole in the bottom? Are you one who sometimes has plants wilt from thirst or more toward the overwatering end of the spectrum? Did your soil say "moisture control?" If you have a suitable spot in the shade to put your plant outside for summer (and don't live where the air is naturally very dry,) that should help get rid of the SM's, if present, also, and all Philodendrons love humidity and warmth.

Are the white spots translucent areas that go through the whole leaf, so you see them underneath too? If that's the case check for pests eg.spider mites, that damage the leaves when they suck (chew?) on them from underneath. If it's powdery and wipes off, how about powdery mildew? Or could the spots be from something sprayed on or near the plant? Just thinking aloud here, hopefully someone who has seen this problem will be able to help :)