They are on the wrong paper ,yours are on white paper ,the originals are on thinner grayish paper .
The Faridkot 1888 ŻA reprints were printed on white
wove papers which unfortunately in Indian climate tend to yellow easily. That is why most of the stamps are found on toned/yellowed paper.
Ref. The Stamps of Faridkot
Edward Benjamin Evans.
The Philatelic Journal of India (Vol.XLIV No.9 9/1940)
Also the forgers used different shade of ink than the originals .
The first stamp you show ,the blue should be more ultramarine , the green stamp should be emerald green in color .The black stamp should be more gray and not as dark , and last the Orange/brick red stamp should be more rose in color .
Shades are the last thing one should consider if an IFS stamp is genuine or not.
(Courtesy my friend Mahesh Madduri)
There are several shades of the same color of Faridkot reprints and there is no rigid rule of color to determine the genuineness of IFS stamps. It was not a one time printing in 1888, rather series of several printings, done at least till 1899, resulting in different shades.
Faridkot posthumous reprints are found in abundant quantities. Every IFS starter pack invariably contains one or two of these. On the contrary, forgeries of the reprints are less common than the so-called "original" reprints, most common among the forgeries being from the modern "Ilahabad" forger's factory.
AND LAST -----these stamps have very fine detail in the design and the four you show are blurred ,design is very fine in detail and stand out with fine detail .
This is not that simple.
By this logic, the following Faridkot stamp should outrightly be labeled as forgery.
But it is not. Guess why?