I have recently bought a devil's ivy plant. I have put it out on our balcony where it gets about 4 hours of sun a day. I have noticed that there are grey marks on the back of the leaves and in a couple cases they are on the front as well. I have only had it about a week and a half and watered it when it arrived. I have checked the soil and it doesn't need to be watered again.

I have another devil's ivy plant about 2 meters away from this one and it's thriving.

Has anyone seen this before?

Move it back inside ASAP. Your Pothos is a low light plant that grows outside in deep, deep shade. That is why it does well indoors where the light is greatly reduced. It needs protection from direct sun even inside.

Thank you so much for the advice. I had no idea sun was bad for this little guy!