Fonts rendered through textures look thinned
From looking at your example images this looks like a case of Alpha blending being applied to the RGB channel of the font-atlas texture and then again applied via the A channel when rendering. 

The tell-tale sign of this is usually a feint dark halo surrounding your glyphs which is caused by the unwanted mid-greys present in the texture being multiplied by alpha.

For font rendering it is typical to have anti-aliasing in the A channel and have your RGB channels a constant colour.