Perhaps you've been playing before and realized that some notes have a different feel and playability to them. One note is harder to press, and the other is lacking response and dynamics. Your piano likely needs a regulation. Regulation is the adjustment of all the moving parts within the piano action to ensure a consistent touch and feel of your piano. This is done by adjusting each mechanism and fine tuning their ratios to each other. That way your piano always plays with the proper control of dynamics, repetition, and tonal quality.