Yeah, it had to be something fairly simple because you were doing everything else correct, and I should've picked up on that early on but didn't. As far as amperage, what you need to calculate is the maximum amp you might be pulling. So, on 115 LEDs, that 115 * 60mA = 6.9A and on 134 that's 134 * 60mA = 8.04A. So no, you won't need a 30A power supply. And this is assuming a full 100% duty cycle on all three channels.
In my case, I create installations with quite a few more. The 30A PSU allows me to put a maximum of 500 of those LEDs. But, I always keep it below that with no more than 15 meters (3 reels), or 480 LEDs. That runs about 28.8A ... I have 1.2A left to run a controller with whatever peripherals ... 
As for power injections, I try to inject power every 3 to 5 meters, depending on the total length of the string.
Glad to see things working now.