I'd be very cautious about the claims of Sturrock and Fischbach. 1) these guys are "fringe" scientists whom some would label "crackpots" 2) they did not do any of these experiments themselves, but are re-analyzing the data of others. Hence, they may be missing crucial details in how the experiments were set up. 3) others have re-analyzed the same data and claimed that the signals these guys see are not there 4) one of the main signals that these guys see is an annual variation. Annual variations can have any number of alternative explanations.
My bet is that they are not seeing true variations in the decay rate at all. I'd bet on an instrumentation problem, where the decay measurement has a slight temperature or humidity dependence, giving rise to a false annual signal.
"Science without religion is lame, religion without science is blind." — Albert Einstein
I am very astonished that the scientific picture of the real world around me is very deficient. It gives us a lot of factual information, puts all of our experience in a magnificently consistent order, but it is ghastly silent about all and sundry that is really near to our heart, that really matters to us. It cannot tell us a word about red and blue, bitter and sweet, physical pain and physical delight; it knows nothing of beautiful and ugly, good or bad, God and eternity. Science sometimes pretends to answer questions in these domains, but the answers are very often so silly that we are not inclined to take them seriously. — Erwin Schroedinger