Even though the situation is basically resolved now, which is great for you
, I'd just like to mention its most probable cause
so that you don't have to wonder if it happens again...
Occasionally, a thread which a moderator or an administrator deems as SPAM will get deleted, along with all the posts in it, of course. When that happens, the credits of each of those posts will be taken back from its respective member, resulting in a seemingly unjustified credit decrease.
That's why it's advisable that, whenever you see a thread that you believe is SPAM, you don't post in it, even if you're merely warning the thread starter, since this will lead to a temporary (i.e. deceptive) increase in your credit count until the thread is deleted. What you can do is to notify the responsible moderator through the REPORT
button. It'd be a great help, anyway