I would check the glowplugs again. I see that you had a shop replace them all, but lon experience has shown that a new plug is about as likely to fail as an old one at any given time. All it takes is one out and with a rough running diesel already and a little cool weather it will not start.
Just pull the glow plugs and clamp them in a vice and then ground the vice and touch the end with 12v. Will either get red hot or will do nothing.