The enclosure is not bad for a temporary home. Adding a fake leafy vine, over the open area, (& maybe even an extra little hide) would not be a bad idea. Babies, especially, like to feel pretty secure.
I, myself, like to have a bit more holes, in a tub, (than what it appears you have) but opinions could differ.
Cannot quite diagnose the cause of the bend in tail (could be due to one of a few things). However, the necrosis is very like due to having had a stuck shed, at end of tail, which ended up constricting blood flow. This is, of course, not reversible. It shouldn't affect the gecko's overall health and the end of the tail may just drop off.
Baby geckos don't eat a whole lot. This can make it seem that they are not eating.
Although, maybe adding another food dish, on opposite side of enclosure than the other food dish, could help.
Gargoyle geckos are not as avid an insect eater, as Cresties, etc., but you could try feeding appropriate sized crickets, or roaches, a couple/few days per week (in addition to the CGD). If eaten, great. If ignored, after some attempts, you could just bypass offering insects for awhile (or altogether if you wish).
Poops, of babies, will be quite small (usually one tiny "pellet" at any given BM) and can, very easily, be hidden in the bark, etc. (or "smooshed", at some point, when still "soft"). This could be the case here.
However, if you go over everything with a "fine toothed comb", and cannot find any, at all, you may want to revisit the question, as to "why", sometime shortly.
Although, if the gecko is behaving normally, there may not be a problem.
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