For a number of reasons, the normal point of breakage is at the elbow.

Breaking at the head like this is very unusual, and may be the result of a manufacturing defect, but it could also be because the hub flange was too thick putting excess stress on the head.

If it's a manufacturing defect in five of 40 spokes on the same wheel, then it would be safe to assume that large quantities of spokes share the problem. Check for reports of spoke problems of bikes made that year. As I said it might be the hub flange, and the tipoff would be spokes sitting unusually close to the flange face on their way to the rim, or you could remove one and check the fit.

BTW- spoke defects aren't all that rare, some time back, I bought two GV hybrid bikes to keep in Cozumel, MX. All was well for 2 years and wen I went down the third year all four wheels had large numbers of broken spokes. I suspected vandalism and thought nothing more of it. On my next trip I brought a handful of replacement spokes, only to find that 100% of the spokes were as brittle as spaghetti out of the box. Turns out they were made of the wrong grade of stainless steel, and it was highly vulnerable to the Chlorine ion in salt.