PCB multiple ground planes
As far as I understand from your schematic and PCB, you are generating two 3.3V DC and one 5V DC as the output of your circuit and you need isolation from 15V DC and the input that you have used for generating the 15V DC.

IF all of these sources are going to feed a card or a complex of connected cards, you ought to have a single ground plane for all the sources and making separation between grounds may lead to hazardous potential difference between the separated planes that is not good. Separated grounds are OK just if the Power supply card is feeding completely separated cards and none of the cards are using more than one output of the Power supply card.

Based of this, my recommendation is
0. use as unique as possible ground plane (not separated) at the output side of the Power supply card.
1. ensure that the 4 millimeter separation on the PCB under the TRACO is supported. 4 millimeter will give you 4kV isolation.
2. It is a very good practice that near the FPGA connector, connect the screw hole directly to ground and connect the other screw hole to ground plane via low ESR capacitors. Obviously the screw hole is connected to Earth or metallic case.


It seems that copper density at the top layer is high therefore during automatic assembly process it could make bad tensions on the assembled parts. normally you ought to have near the same copper density at the bottom of your PCB too to balance the tension or if the PCB is a single layer one, It is recommended to not using solid copper plane and instead of that, use the hashed copper plane.