Incorrect scoring method

What amazed me is that from January my redit report has shown a good steady growth pattern, The last 2 months I have noticedy score has gone down by 7 points into below average even though my accounts have been paid, then when I query this I am told that my score has gone down because I have paid 2 accounts in full how is it possible to receive a negative listing for paying things off? I have zero debt now and cannot qualify for anything either because I've paid off my accounts!