Congrats on the new frogs ! Did breeder who sold them described their care/feeding schedule while at his charge? How old are them and what is their length from snout to vent? The fact that they where placed in a couple day fast before shipping should not reflect in their weight at all. They look thin; but that might be related to age if very young.

I would quarantine them for 30 days and get two fecals done 2 weeks apart during that period. Love Mossys, good luck with them !