5*r9 270 giga problems (SICK/DEAD)gpu

[orcage]

5 r9 270 gigabyte - GV-R927OC-2GD
2 power supply - thermaltake tr2 750w bronze
motherboard  Asus f2a85-pro
4gb ramm * 2
cpu athlonX2  bla bla bla
hard disk - western bla bla bla  320gb

13.12 amd drivers
windows 8.1/bamt 1.5.2

5cards dont work stability  
sometimes (20min-5hours)  1 of 5  gpu are going to SICK/DEAD
temperature - 66-70 degrees
in windows on vertminer/bamt - one problem sick/dead gpu
910/1350 - work 24h   940/1400 - work 8-16h   970/1450-work 5m-2h and lost 1 gpu
1 week hard sex with thats mining rig

IF HELP ARE REALY work - i transfer to THIS FUTURE MINE GOD 1 vtc ^^