looks like you are doing a great job raising them up man! young gar (especially from that small size/stage) can be quite delicate (although more robust than walleye, pike, muskie), and so your survival thus far is good.
the stage where they are just getting big enough to eat fish is a tough one...you can keep them fed with larger zooplankton, but if you can track down some small minnow fry this will push them to the next stage (piscivory) much faster and get them to grow to a more stable and manageable size too.
keep up with water changes and they should do just fine. be sure to monitor if any of them are getting noticeably bigger than their siblings...they WILL readily eat each other! best of luck, and looking forward to tracking their progress--
--solomon