The usb and BT version should work independent of each other. If the BT version only works when the usb is connected then there is an issue with the circuit somewhere.
It sounds like the Arduino may be taking power from the USB port.
How is the Arduino powered when using BT? Does it work without a usb connection, does the Arduino power light come on when using an external power source?
1. Get a Bluetooth connection working, and then
2. Confirm you can run the Arduino from an external power source, and then
4. Get a BT connection working while using an external power supply.
5. Test the valves by connecting directly to a 12V power source.
Get a simple connection working with the android device. Follow the examples at http://www.martyncurrey.com/arduino-with-hc-05-bluetooth-module-in-slave-mode/
While resolving the issues I would recommend you make a dropController emulator. Bread baords are ideal for this. This is simply an Arduino with LEDs (with suitable resistors) on all the pins used by the dropController. Do not add the optocouplers and TIP120s. This will make testing a lot easier.
RE the valves opening.
You need to check where the power is coming from and if the Arduino pin is HIGH or LOW. If the Arduino pin is low then you have a wrong connection somewhere.
Do you have the valves connected correctly? Do you have the wires the right way around?
Have you tested the valves by connection directly to a power supply?
Are the TIP120s connected correctly?