By John McCrank and Alun John NEW YORK (Reuters) -Regulators opened probes following last week’s spectacular collapse of crypto exchange FTX and rival exchanges sought to reassure jittery investors of their own stability, weighing on cryptocurrencies on Monday. The implosion of FTX, once a darling of the crypto industry with a $32 billion valuation as of January, has spurred investigations by the U.S. Justice Department, the Securities and Exchange Commission and Commodity Futures Trading Commission, a source with knowledge of the investigations said. The SEC probe is also targeting FTX execut…