Ok - well there are a few things in general that you need to change here, most of this is probably a result of misinformation from the petstore.
1. Calci-sand is a terrible and dangerous substrate. Petstores promote it because they have no knowledge of the dangers, and/or because its expensive and brings them a pretty profit. Its been known/proven to cause impactions in a variety of lizard species...I do a lot of rescue work and have seen many lizards with calci-sand impaction. The stuff is not digestable at all, as it claims to be- it clumps together into tight, sharp balls and causes huge issues. Calci-sand is also dirty, smelly, will "stain" your lizards skin and can cause eye infections. Throw it away
All leos under 1yr of age should be housed on a substrate with no impaction risk - i.e nothingthat is loose and potentially edible. Tile, non-adhesive shelf liner, reptile carpet or paper towel are all acceptable substrates. I used non-adhesive shelf liner for YEARS (recently switched to tile) and i loved it. Its cheap - you can buy a big roll at walmart for about 5$, its easy to clean - you just spot clean and toss it in the dishwasher when it gets nasty, and completely safe.
2. Correct temps are vital to Leos. You need to be measuring the belly temps with a digital thermometer. You can buy a digital thermometer with a probe at walmart, home depot or petco. You take the probe of the thermometer and tape it to the floor of the tank over the heat pad. This reading should be 88-92degrees. The dial type thermometers are very inacurate, and are also not measuring the belly temps - which are the most important. Most heatpads get very hot - using a substrate such as tile or shelf liner or paper towel, you will probaby find the heat pad alone heats the tank to over 100 degrees (depdning on the brand of the heat pad). If this is the case, you will need a dimmer device so you can manually control the heat being put out by the heat pad. When you go out to buy the thermometer i would save a trip and buy the dimmer at the same time. You can buy a plug in lamp dimmer at home depot, there is a section for lamp dimmers and there is usually one plug in variety. These are cheap and easy to use. You simply plug them into the wall and plug the heat pad into the dimmer, then you use the dial on the dimmer to tweak the temps of the heat pad.
3. Leopard geckos rarely drink from their water dishes, so supplementingthe water wont do them much good. Their primary source of calcium and vitamins needs to be from dusting. You will need three different types of dust for this. a) a pure calcium carbonate dust with no phosphorous, no d3, no vitamins. b) a calcium carbonate supplement with d3. c) a multivitamin supplement. I personally like Rep-cal or jurrasi-cal/jurrasi-vite brands. For baby Leos you need to supplement daily with pure calcium, 2-3x per week with calcium with d3, and once a week with a multi-vitamin. Good supplementation is essential for good health!
It sounds like a lot, but the above changes are needed to keep your Leo happy and healthy. Once you make them, the set up will be pretty permanant and you should nothave to do a lot more tweaking.
Good luck!! Feel free to keep asking anymore questions 
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1.1 Bearded Dragons
2.2 Leopard Geckos
1.0 Uromastyx (Mali)
1.1 Corn snakes
0.1 Mexican Black Kingsnake
1.0 Bairds Ratsnake
1.0 Rosy Boa
1.1 Green Anoles
1.1 House Geckos
0.0.2 Flying Geckos
0.0.1 Red Eye Tree Frog