3 Boards blown in all same spot

I has recently sold my setup and the gentleman that bought it has blown either 3 or 4 boards within 2 weeks... he said all in the same spot!!!! ( you can see the damage) the setup is as follows
Asrock h81 pro btc
ax1200
g1840 cpu
8gb ram
80gb ssd
Gigabyte r9380 4gb cards
non powered risers.
I had been runing this setup for over 6 months with no issues.
Any ideas as to why he keeps blowing them?