On the online OCI application you have to follow:
- Country of Birth (Drop Down Option)
- State of Birth (Drop Down Option)
- City of Birth (needs to be typed)
If you have mentioned that you are married but do not include spouse details is inviting trouble for yourself and chance for BLS to make money on your expense. Remember this is not a visa this provides you more or less a permanent status to travel to India etc, so you declare relevant details. Flip things around, didn't you declare spouse status/info when immigrating to Canada ?