Are they still as active? It seems they have entered brumation which is common in the winter months but they shouldnt really be losing too much weight from that. Raw egg is good to drip over food as an enticement but dont over do it cause some people have had problems with their skinks afterward. You could also try babyfood.

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0.0.1 Corucia (Bubba)
1.0 Indonesian Blue Tongue Skink (Don)
1.1 Irian Jaya Blue Tongue Skink(Sammy) & (Sausage Girl)
0.0.1 Tanimbar Island Blue Tongue Skink ( Spunky Sebastian)
0.0.1 Ornate Uro (Spike)
1.0.1 Green Tree Pythons ( Male=Floyd, Baby= Verdi)
0.1 Western Hognose (Piggy)
0.0.1 Egyptian Tortiose(Tank)
0.0.1 Sonoran Gopher snake ( Toro)
0.1 Albino Leo gecko (Sasha)