Sometime between last season and this season my mission fig tree has developed some cracks in the bark at the base of the tree. It's a bit hard to see in the pictures, but those crack's go into the core of the tree and it looks dead inside in that area. The rest of the tree is not looking so hot either. I've had it for about six years now, and although it's been living in a pot the whole time it seems to have done well until recently.

I'm in Southern California so it did not get too cold or anything this winter, though it did rain a lot. I think it's had proper drainage though. Any ideas what else it might be?

As a side note - I had a younger potted apple tree right next to it that had a similar issue with its bark but declined much faster and I had to get rid of it a few weeks ago. Not sure if there's any relation but it did seem suspect that they both had issues.