Is your leopard a juvie or an adult?
I dont think i have ever seen a leo that actually looks fat one day and thin the next...unless it was maybe a very thin gecko who only looks fat when full of insects???
Do you have a camera? If you can snap a pic then folks can tell you if generally your leo looks healthy or not
Your set up sounds pretty good, although as Leolady said you should have the UTH on all the time.
What are you using to measure the temps? Are you measuring the temps on the side of the tank or on the substrate floor?
Generally, how is your leo behaving? Where does she spend most of her time - in the warm hide? The cool hide?
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0.1 Bearded dragon (Hannabil)
0.1 mexican Black kingsnake (Morticia)
2.1 Leopard Gecko's (Pogo,Jeffrey Nothing, Louise)
0.0.1 Tokay Gecko
0.0.1 Reverse Okeetee Corn (Autumn)
1.0 Blood Red Corn (Virus)
0.0.1 Mali Uromastyx (Scuttle)
0.1 Bullmastiff (Asha)
4.1 Cats (Poe, Tucker, Abhid, Felicity, Emmy)