birth defects in froglets??

[loudmouse]

First off, Hello! I'm new and came here for some input on my fire belly toad froglets.
So I bred my fbts, well let's be real, they bred themselves, and continue to breed themselves every 3 or 4 days. I only kept the first batch of eggs, moved them to a new tank and succcessfully hatched them and fed them to froglet stage. This is my first time breeding amphibians, and I have to say, watching the development from egg to froglet is one of the coolest and most fulfilling experiences I've had to date. I have lost one to spindly leg syndrome. He wasn't eating enough, and therefore obviously deficient in calcium. After reading about it I figured I'd lose at least one, so though disheartening, it was expected.
But I also have 2 little guys that appear to have some sort of defect. Their bottom jaw is not flush with their top, rather, it remains open, leaving a small opening at all times. Amusingly it almost makes them look like they are in a state of surprise at all times, and they are kinda cute. Anyway, due to this, they can't properly hunt fruit flies, as the bugs can just hop back out of their mouths before they can swallow. I know the surest bet is to euthanize, but for curiosity's sake, I have been hand feeding them frozen and thawed blood worms. (Though I know that this is only prolonging their lives until they do die, or that if they do survive, I might have to hand feed or assist in feeding for life) I use tweezers to put it into their opened mouths and wait for them to swallow, then give them a second one, and I do this once day. This seems to be going alright, one even is starting to gain back some weight. They seem to have no other problems with quality of life, are able to swim, hop, explore etc.
So I guess my question is, has anyone else ever seen this? Is it common? Is it a birth defect or is it signs of something more serious. Should I be worried about my other healthy froglets? What did you do about it? Is anyone interested in updates about these guys? And why/how do you think this happens? My speculation is, since they were normal tadpoles that could eat just fine, that perhaps upon morphing they didn't go though a full transformation from tadpole mouth to froglet mouth.
I'm also wondering if, provided they do survive and are able to grow, once the bugs they eat become larger than their mouth opening if they will be able to eat on their own, or if I'm just too hopeful.
I can try to post pics but my phone camera is junk so they may not be great, though this emoji is a surprisingly accurate depiction lol