your PSU's won't handle all that cards. you definitely need additional power 
Say what? How on earth do you come to that conclusion? Lets see your math. Ill show you mine right now.Rig with 12 1070Ti's at 150 TDP each. (No overclock or TDP adjustments) https://www.buriedone.com/hashrates
if I understand OP right - 1070's run fine, but there are issues with 2x 12x1070ti's rigs. I am pretty sure this is related to additional power that Ti's require.