It is certainly a much higher failure rate than I expect, but it could just be bad luck.

The Toshiba drive was effectively dead on arrival, it died a couple of weeks in.

It isn’t environmental, the server has been in the roof space above our kitchen. The temperature in there rarely moves out of the 20-25 C range and it is never humid.

In comparison my old servers lived in the garage at our old house, with the temperature ranging between 0 and 40 C with humidity often over 90%. The steel on the cases was rusty after 10 years, but all 8 drives kept on chugging along