first of all u should tell us what blending u are using => post some code

I have two+ different textures being rendered onto of other ones, but they don't "blend" correctly, and put in 1-2px "stitch marks" at the edges of the texture.

I tried putting them together from their loaded files in Photoshop, and the dark edges aren't there, so it has to be something between loading the textures, or displaying them.

Even moving parts to completely on top of other parts, they still show dark edges (such as the shoulder and the neck area above).

Are there any blending options I could change to allow it to blend edges better, or something else that would need to be changed?

Thanks!

I don't believe you have a problem with "blending" per see. What usually happens in these cases is that you forget to offset your uv by half a textel. I.e. say the uv's are 0-1 and the texture is 0-255 (i.e. 256 wide/high). When you map the UV's, 0 does not equal 0 in this case. You want the center of the textel to be mapped to 0,0 which in this case is not 0=0 as 0 in the case of the texture means the "edge" of the textel and not the center. So, the edge u or v should actually be set to, assuming u: u=1/256 (or maybe 255, always forget). Without the offset you blend to black at the edges. Or, you blend to the other side of the texture which means you blend to an incorrect color which will make the seam visible also.

hope this helps, if you need more information, let me know.