Claire, are you trying to mix your own Flexicolor (C-41) developer? If so, there are a lot of bad ones published that can lead to inferior results. The same is true of published E6 formulas. Please make sure that you don't ruin good negatives. Test your formula by making enlargments of test objects first to insure good color, good curve shape and good sharpness.
And, please don't try to use it for color paper. Pat Dignan, many years ago, published data showing how it degraded dye hue and dye stability when used in color papers.