Monstera Deliciosa - a multitude of problems

I am driving myself crazy trying to find out what is wrong with my Monstera Deliciosa. After all the research I've done I still can't find an answer to what the problem might be.

When I got it a couple of months ago it was perfect although maybe a little banged about in the store. I re-potted it into a mixture of soil, spagnum moss, perlite and coconut bark and gave it a support pole.

Slowly there have been brown spots forming. They start from the underside of the leaf, then show on the top side. Initially the brown spot is soft and then crisps up. Some are small, some are huge. There are no obvious bugs or insects. The smaller leaves on the bottom are going yellowy and floppy, but the bigger leaves are turning darker and seem to be taking on a leathery appearance. All leaves are developing the brown spots, and the one large leaf that unfurled since I've got it also had the brown spots.

It's on a humidity tray, grouped with other plants and in my opinion isn't over or under watered. Initially I had it on the landing underneath a high east facing window so light wasn't directly on it. I since moved it when it started showing signs of not being happy and it's now in the middle of a north facing living room.

Any ideas anyone as it's stressing me out!

I have been trying to add pictures but they're not showing. 

Last edited: 20 February 2018 19:14:40