You wrote:
"But there was no reason to come forward with it. The matter was resolved when we married."
If you said similar things to JC, it is clear that they had to disfellowship you due to lack of repentance. Marriage did just mean that you stopped committing sins, but marriage did not mean that the matter was resolved.
Just as an example: Someone goes to supermarket and commits shoplifting. The next day, again he goes to supermarket and commits shoplifting. The day after, again, he goes to supermarket and commits shoplifting. On the fourth day, he goes to supermarket and buys some goods regularly, without shoplifting. Does this really mean that now, on day 4, he has resolved his previous crimes? No, he just stopped sinning. But repentance would bring him to confess his previous sins.