Might wanna try f/t one or two more times before you go to live because they're big enough for it not to matter if they miss an extra meal or two, and make sure everything is nice and secure and they arent roaming during the day. The 30 g loss is probably just poop.

If the breeder you got them from was feeding f/t consistently, then chances are they will take it eventually. Use a scale to track their weight, but if they refused another two or three times I would probably try live just to get them going.