Welcome to the forum...I'm sorry that your baby isn't eating, she's quite small and definitely needs nutrition, and she does look quite weak.
I have 2 questions for you that are extremely important, the first one is going to be EXACTLY what
UVB light do you have, meaning the Brand, the Wattage, and the Type, meaning is it a Compact, and Coil, an MVB, or a long tube. I too see a Compact/Coil light next to another Compact light, so this looks like you have a regular Basking Bulb and then your
UVB light is also either a Compact or a Coil
UVB bulb, which is most likely inadequate, and it's also sitting on top of the mesh lid, which is blocking about 40% of the already far too weak compact/coil
UVB bulb, if that's the case. We may be wrong, but the #1 reason that young babies do not eat and become lethargic is inadequate and/or incorrectly mounted
UVB light.
The second question is about your temperature readings...you said that you have a "Strip Thermometer" on the back of the tank on the Hot Side that is reading 100 degrees...I'm assuming that by "Strip Thermometer" you mean one that is a stick-on? If so, then this is a HUGE problem, as it is NOT reading his Basking Spot Temperature, because if it a SURFACE Temperature that can only be read by a Probe or a Gun. If you have a stick-on strip thermometer on the Hot Side of the tank, stuck to the glass, and it's reading 100 degrees, that is actually the Hot Side Ambient/Air Temperature, which is WAY TOO HOT, it should only be between 88-93 degrees F maximum.
So regardless of how you measure the Basking Spot Surface Temperature, which should be between 105-110 degrees F maximum for a young baby, the fact that you have a stick-on Strip Thermometer on the Glass in the back of the Hot Side of the tank that is reading 100 degrees F is absolutely the Air/Ambient Temperature on the Hot Side of the tank...This is most likely making him extremely dehydrated, and will also certainly make him tired, have no energy at all, and have no appetite at all. And the other issue is that if the Hot Side Air/Ambient Temperature is reading 100 degrees, then the actual Surface Temperature of any solid basking spot/platform located within that Hot Side of the tank is going to be much higher than the surrounding Air/Ambient Temperature....