Quick LED Strip question...

Greetings! I've got ~4m of RGB LED strips in this project (in short, the Arduino listens for messages over serial and enables/disables the various channel outputs (3 wires per channel) via MOSFETs. First off, the 12v/15w PSU is connected to the Arduino's GND and fading via PWM works perfectly on all of the strips in each channel. It's all working just fine (as well as I need it to, anyway) when 3 of the total 4 channels are in use. Each channel functions just as it should when activated independently (shelf by shelf), so I am fairly positive that this is not a wiring/connectivity issue. When I activate the 4th channel so that all strips are on, the entire system just goes spastic and all of the strips blink intermittently; As soon as I drop it back to using only 3 of the 4 channels, it works just fine. I think the issue is due to insufficient power, but I wanted to run it by as a topical subject before I go scrambling for the info of the components in use... Thoughts?

4 meters of RGB strip and only 15W power supply might not be enough. If the power supply getting hot with only 3 channels ? How is the Arduino board powered ? Can you use usb power for the Arduino (or a seperate power supply) and the RGB strips with the 12V power supply. Use a multimeter to measure the voltages and the current.

Thanks for replying, though strangely enough, the issue seems to have dissipated... I'm confused, but not arguing the fact that it's working. haha