It's perhaps a bit more suspicious with Altuve than Blackmon... Altuve had three seasons of 500+ ABs and never hit more than 7 HR, then jumped to 15 and then two seasons of 24. Blackmon didn't have a season of even 300 ABs until 2014, but that year when he got 593 ABs he hit 19 HRs, then 17, 29, and 37 in the following three seasons.

At any rate, there's more than just one conclusion that can be drawn from stats like those. PEDs is one conclusion, but maybe some guys just find their power later in their career? Up to age 36, Tony Gwynn had two seasons where he hit more than 10 HR (14 and 12), and then hit 17, 16, and 10 at age 37-39. Does that lead to only one conclusion? I think if you look at a pic of  Tony Gwynn ca. 1997 it will be tough to argue that steroids had anything to do with his body. More like Little Chocolate Donuts cereal.