All the Credit Reporting Agencies Have Different Reports On You
All of these companies have different reports on you. This is because they don't share information about you with each other. They are competitors with each other. Each wants their own information, it's how they make money.
Suppose you apply for a loan, line of credit or credit card from a lender. That lender almost certainly performs a credit check, requesting that a report on you be run, from at least one of the three major credit bureaus. But it does not have to use all three. The lender might have preferred relationship or value one credit scoring or reporting system over the other two.
All credit inquiries are noted in your credit report, but they only show up for the bureaus whose reports are pulled. If a credit inquiry is only sent to Experian, then Equifax and Transunion do not know about it, for example.
Similarly, not all lenders report credit activity to each credit bureau. So a credit report from one company can differ from another. Lenders that do report to all three agencies may see their data appear on credit reports at different times simply because each bureau complies data at different times of the month. Delinquency generally doesn't affect your credit score until at least 45 days passed.