String and/or cables have stretched. If you know or can find out the bow's specs measure the axle to axle length and brace height. I'll bet the brace height is low and the ATA is long. When this happens it reduces the preload on the limbs with the result being a change in draw length and reduction in draw weight.

Depending on how far off they are you could have them retwisted to bring up to specs or replace them.