I'm quite sure you signals in the 4 paths are out of phase, and don't add up.
For each of the amplifier paths through the couplers, you should write down the total phase offset from the couplers.
I round your phase results a little bit and get these phases at the input of the amplifiers: 90°, 180°, 90°, 0°.
If use the same couplers on the output side, the phase offsets double: 180°, 360°, 180°, 0°
In other words, the signals from the 4 amplifiers cancel at the output.
You need to compensate the phase offsets by extra line length in some (not all!) paths, so that all paths are in phase at the combined output.