Hi and Welcome....I know the conflict with work schedules can interfere with babies, if you can bottle them b4 you leave then put there bottles in a tube sock suspended from the pen so that they have access to a mid day bottle, feed again when you get home and then before you go to bed. If you work 8-9 hours a day, you can easily transition them by giving them their bottles in the evening hours and making your work hours their "sleep" time as moms don't usually feed their kids at night. Make sure they have a pail of water and freechoice hay available at all times .
Example bottle feeding: 10oz each kid at 7 am( pretend this is the last bottle of the "night")
10 oz ea kid at 5pm or as soon as you get home, then another at 7pm and one at 10 or 11pm. As far as the replacer, if they stop getting diarrhea after you begin spacing bottles then stick with your water/powder formula, if they continue you may have to adjust the ratio.