Since losing the one to sls, I've been using the same calcium duster powder I use for my adults. Before that, I'll admit I was slacking. I noticed this problem after they morphed. Before they morphed they would only eat algae and fish flakes, they didn't seem interested in anything else. I'm not sure how one would supplement the algae pellets and fish flakes, so I didn't. So maybe supplementation was the problem, or maybe they should have been eating invertebrates before they morphed as well.
As a side note, all of the other froglets are growing, healthy, have a voracious appetite and are starting to develop their green backs and orange bellies.
I'm wondering whether perhaps the parents may have been related and if that has anything to do with it. They were purchased at petco at the same time. So honestly I wouldn't doubt it. I won't be breeding the offspring, just wanted to raise them, keep 2 more to add in with my adults in their 20 gal, and then give the rest to friends/lps. I will note, it was never my intention to breed them anyways. They did it all on their own after their tank upgrade. And I have been scooping out and throwing away any eggs since the first batch, call me plan B lol.