I doubt that a 7 1/2 watt bulb is providing much, if any, heat for your geckos. If you are going to be using such a small bulb, I would get a UTH as well.
Be VERY careful with the dirt/soil. Actually, I would get rid of it. It can be full of bacteria, chemicals, and retain too much moisture. As for the plants, it's very difficult to maintain a plant with leos because they like to walk all over them. The only plant I've had survive is a very thick and stumpy succulent. All of the dirt for the plant in my tank is covered by fairly thick layer of rocks, so the gecko can't get to the dirt.
It may sound creepy...but you might want to try roaches. They can be expensive to buy constantly, but are great if you breed them. Leos (usually) LOVE them. It's great that you are trying other feeders, but sometimes the leos become very picky and will only eat a certain thing. So long as it's not waxies, then you should just live with it. One of my girls won't eat anything but mealworms. I try every now and then to feed her other things, but she's just not interested.
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Official Leopard Gecko Freak
1:1 Leopard Geckos - Gilean and Aurora
2:0 Cats - Troi and Mitsu (shhhhh...don't tell them they're neutered!)
4:0 Betas - So pretty, yet so violent!
1:0 Husband - Eric (He's a lot of work, but it's worth it.)