I think the term soil needs to be eliminated here. Fox Farm's Ocean Forest is not soil, it's not dirt, it is a soil-less potting mix. They do indicate they add sand but there would be trivial amounts compared with say a well balanced garden soil or loam. OF is meant to be light and airy just like all potting mixes so the plants can breathe. If you were to use soil in a container the roots would not have any room. The compaction would be so great you would essentially be creating concrete. I'm not saying it is as light as say seed starting mixes but they should really reconsider the use of soil on their products.
Think of potting mix as a room and the nutrients, trace elements are the furnishings. It's the basic environment. You can certainly replenish tired potting mix by adding the things that have either broken down or have been spent up. We're talking about a weed here that is pretty hardy. So it's not extreme rocket science. It's just that you will have to mix things up because a potting mix is not a total living environment like the soil in your garden. It's missing one of nature's tireless workers, the earth worm. In your garden you can top dress and let the worms bring the organic matter down. So mix in some new earthworm castings, some guano, test PH and adjust accordingly. Again this is a weed, it has learned how to thrive in the worst of environments. The thing is if the second use doesn't turn out as well as the 1st and you're prepared to blame the mix then you might as well get new potting mix. JUst don't dump the old stuff in the trash. If you have a garden side dress some plants or toss it in the compost pile.