This is crazy. I ordered fifteen (15) cards from Newegg.com for $249.99/ea and that was in December!. The crappy part is how I had to order them in groups of three. Wait 48hrs. Order three more, etc. I did the BIOS mod and I'm getting 29.8 MH/s per card average for the Samsungs, 28.7 Hynix, and 24.66 with the crappy Elpida memory. Thank God that almost all were Samsung!
(off-topic) You do it wrong with elpida memory, I get 31+.
(on topic) As it has already been suggested, send them back and get 1070Ti instead. The only RX580 advantage over 1070ti is that they are twice cheaper !