Either get more miners to dbix3, and/or reduce the N to the expected pool hashrate.
Also, I not make 3 pools for the competition but for network security, I prefer 3 pools with 200ghs each rather than 1 with 600ghs
I think there is a too huge difference between the pools, if you raise dbix1 to 5000 or 10000 and lower dbix3 to 50000 it would split up a bit more