Crosstalk in PCB layout
In most cases, it's a bad idea to separate GND planes. What happens is that you have high-frequency noise going around and you end up having your 3 planes behaving as 3 capacitors coupled to your inner plane.
It is also very difficult to guess where the high-frequency noise/current goes as it doesn't necessarily follow shorter paths.
Another issue is that it is a bad idea to have traces running through a plane gap (which would be the case in your design). This couples the trace between the planes.
If you want to make a low noise plane for analog, the best method is to split the plane in half (and not having several planes across the board), filtering from GND to AGND, and connect the plane beneath what does the AGND to GND link like ADC and the power lines (through R-L-C filtering).
Overall, in most real-life cases, you will end up with less noise using a single plane, well done multiple planes can be better but they can be tricky.
It is also better to have all the connectors on one side of the board to avoid cross current flow.