It is nearly impossible in any given situation to determne when or if your scoring has been moved to a different algorithm based on a general categorization of a given scoring category (also know as a scoring bucket).
The criteria used by FICO to place your scoring of a given category into a new bucket, such as maxed-out util, clean vs dirty, thick vs thin, new vs non-new, etc. is a closely guarded trade secret of the FICO algoritms.
The best that can be said is that if you cannot attribute a score change to any speciific new information, then it might be due to a new algorithm being applied to your scoring based on a subtle change in some general categorization. Age of accounts is a normal change that always increases from time to time that might result in a re-bucketing of that scoring category. Other rebucketing, such as become clean in pament history (i.e., no major derogs) are usually very obvious.
