It was that the factors that gave Britain an edge were being removed as other nations developed (caught up). Industrially Britain got caught out in some ways from having too much invested in early adoptions of technology while late adopters were able to invest cheaper in later and better technology. It's all rather natural there is no real reason for Britain's advantages in the 19th century being long lived, the decline in it's advantages was all rather natural.
There's a lot of truth in that I think, but it is also the case that Germany in particular was much better at exploiting scientific advances for technological and commercial purposes (one only has to think of how Germany came to dominate the market in synthetic dyes). In Britain there was something of a disconnect between basic research and industrial application. This is a good summary of the situation in Germany:
"The
German Empire came to rival Britain as Europe's primary industrial nation during this period. Since Germany industrialized later, it was able to model its factories after those of Britain, thus making more efficient use of its capital and avoiding legacy methods in its leap to the envelope of technology. Germany invested more heavily than the British in research, especially in the chemistry, motors and electricity. The German
cartel system (known as
Konzerne), being significantly concentrated, was able to make more efficient use of capital. Germany was not weighted down with an expensive worldwide empire that needed defense. Following Germany's annexation of
Alsace-Lorraine in 1871, it absorbed parts of what had been France's industrial base.
[39]
By 1900 the German chemical industry dominated the world market for
synthetic dyes. The three major firms
BASF,
Bayer and
Hoechst produced several hundred different dyes, along with the five smaller firms. In 1913 these eight firms produced almost 90 percent of the world supply of dyestuffs and sold about 80 percent of their production abroad. The three major firms had also integrated upstream into the production of essential raw materials and they began to expand into other areas of chemistry such as
pharmaceuticals,
photographic film,
agricultural chemicals and
electrochemicals. Top-level decision-making was in the hands of professional salaried managers; leading Chandler to call the German dye companies "the world's first truly managerial industrial enterprises".
[40] There were many spinoffs from research—such as the pharmaceutical industry, which emerged from chemical research."
From here:
[ame="http://en.wikipedia.org/wiki/Second_Industrial_Revolution"]Second Industrial Revolution - Wikipedia, the free encyclopedia[/ame]
It is not that the springs of invention dried up in Britain, but that much more reliance was placed in that regard on individual enterprise.
As for the OP's suggestion that there was a decline in scientific research in Britain during this period, that is actually the reverse of the truth.