If it had been dormant for 3 years and then had activity that would cause a drop. The good thing now is it will start to age and you should not see any more drops. What other baddies are on your reports. This may have been the last open collection, but with other baddies you won't see much increase until they fall off the report. Did you negotiate a pay for delete or which company is this as some will automatically remove after a certain time if they are paid? Paid is always better than unpaid, but if it's still showing up on the reports then any gain is muted.
Where are you getting these scores from? If they are vantage from something like credit karma then they don't follow the same algorithm as the Fico scores and really don't matter much. With scores in the 5's then there are likely other things on the reports that are still holding you in the lower score cards.
