I can't tell from the picture what happened. But honestly...just throw it away. The Apex is a nice tank until it starts leaking, then it's done for.
If you have a bunch of extra isub coils that you want to salvage like me, you can get their new iSub V tank from myvaporstore for only $15. Similar vape to the apex. So far it does the job, but I assume it'll fall apart like all their others soon enough. I don't recommend giving them anymore money...but like I said, if you have extra coils, might be worth the risk.