PCB routing of SPI lines
This doesn't look to bad. It would be important to know the SPI CLK frequency. First try to reduce the frequency of the SPI Bus to see if you your problem is getting less sever.
My first guess would be rather some pins that are not set correctly or wired wrong. If you can try removing a slave at a time and see if that solves your problem.
With the attached picture it is quite hard to give advise. If you can share the board file you are more likely to get some help.