This would be my suggested algorithm, which would allow for you to indicate which forums are part of the streak:

Create a new DB table to hold streaks. First column, is the alt’s ID#. Second column is to hold the forum ID# of any forums currently on the streak. One row per forum. The table is keyed on both columns.

Every time you complete a forum successfully, the system tries to insert a row for you and that forum. If it gets a duplicate key restraint, that means you broke your streak. All records for you are deleted from the table, and a new row is written with this most recent forum (the start of a new streak).

Then you do a “SELECT COUNT(*) FROM <table> WHERE user_id = <userid>”, and divide the result by four. If there’s no remainder, award the appropriate peen and scoops for that result number.

If you fail to beat a forum, the system deletes all rows in the table for you.

That’s what I’d do.