Tiny lines appearing in a repeat pattern where it has been cropped

I have been making repeat patterns for fabric and wallpaper for about 8 months now.  I use Illustrator on my IPad to create the repeat - using the grid function.  Then I transfer the file to Photoshop to touch it up, crop it and resize it.  There are thin lines in the repeat where I have cropped it.  They don't appear on white or very light fabrics - but they are on most of my patterns.  When the designs are printed onto either fabric or wallpaper the thin lines show. I cropped a few designs in Photopea, just to see if the problem was me.  There are no lines when I crop in Photopea.  So the problem is Photoshop. 

Is it possible that something about the grid function on IPad Illustrator is causing the lines?  I really don't understand why I have the lines.  

You can see them in both of these patterns.  Even the faint line in the purple is visible when printed.  I am super frustrated.  Thanks for anyhelp someone can give me.