Even with correct time, there needs to be 100ml of the undiluted Xtol in the mix. Be sure you follow that. If your tank needs 250ml per roll to cover the film, and you did Xtol 1+3, you'd think you only need 250/4 = 62.5ml of Xtol and the rest in water. You'd not have enough Xtol to do the development.

Trust me on that one