The fakes of these issues tend to be counterfeit surcharges on genuine stamps. (If we're dealing with the surcharged Armenian pictorals instead, then fake surcharges on fake stamps abound, but they tend to be the easy one to spot.) None of these are on watermarked paper, I believe.
These are three of the most numerous of the 1919-20 Armenian surcharge varieties, so you've got a decent shot at them being legit.
This blog by a knowledgeable collector has interesting discussion about these issues, including literature tips, signs to look for on a forgery (most higher value surcharges and postally used material on the market are fakes), and analysis of individual Armenian items found on
ebay or auction houses:
http://www.stampsofarmenia.com