Until Sin Cara failed a drug test in June that got him suspended in July when he couldn't provide an adequate prescription for the banned substance, no WWE talent had officially been suspended since Rey Mysterio two years ago in August 2009.
You can speculate all you want about the reason that there were no official failures/suspensions for almost two years and then three (with one not officially announced) within a month or two. WWE added synthetic marijuana substitutes like K2 and Spice to the banned substance list in late June.
Presumably due to the substitutes being more dangerous and occupying an odd space legally, they are not punished with a fine (and unofficially a decreased push) like marijuana or alcohol, instead garnering a suspension like all other drugs.
The change came after Sin Cara's positive test (believed to be for anabolic steroids) is reported to have taken place, so it might not mean anything for him, but it could for Chioda and Leavine.
Still, even then, knowing the wrestling business, it seems really strange that nobody could fail a drug test for two years and then three would be failed so close together. Also, it seems like the key wrestling reporters are in agreement that Leavine has been suspended even though it hasn't been announced yet.
That is also...curious.
At any rate, something's happening, and it's the latest bump on the roller coaster ride that has been drug testing in pro wrestling. The topic has a fascinating history, one that I will try my best to condense for you, the reader.