Do you know the current draw from each of pca9685 pin? I would be very concerned if you are not powering it with dedicated 5v line.
I may be wrong, but isn't the current draw limited to only 25 mA from each pca9685 pin? From the datasheet: The PCA9685 operates with a supply voltage range of 2.3 V to 5.5 V and the inputs and outputs are 5.5 V tolerant. LEDs can be directly connected to the LED output (up to 25 mA, 5.5 V) or controlled with external drivers and a minimum amount of discrete components for larger current or higher voltage LEDs.