Turtles/YBS is getting a soft shell
Hey okay so i have a baby yellow belly slider and a baby map turtle i got them a few weeks ago i keep them in a ten gallon tank right now with a heat light filter water heater and a place for them to get out of the water. I got the whole set up from walmart it all came together. today i woke up and went to check on them and the yellow belly was on his rock in the heat its his favorite spot he didn't eat last night so i woke him so he could and i noticed his shell is soft on the sides... i had assumed the heat light was also the UVB light but now im not so sure. im wondering if its an easy fix maybe if i could just add another light or get the calcium stuff to rub on his shell?
ps. i feed them the floating sticks and shrimp right now
UVB is extremely important, and if you got the setup from Walmart, it's highly unlikely the basking bulb provides any UVB. The first thing I would do is get a bigger tank. 10 gallons is too small for one hatchling--20 gallons is the bare minimum, and really I would get a 30-40 gallon tank so you have room for them for at least a little while. Keep in mind you will need a much bigger tank (with matching filter) within a few years; for the turtles you have, you'll probably need a 125-150 gallon tank.
I would recommend get a ZooMed Powersun bulb. It's a combo heat//UVB bulb that gives off good amounts of UVB, and needs to be replaced yearly. The only other UVB bulb I can recommend is a tube bulb (Reptisun 10.0), which needs to be replaced every six months. I don't know of anything you can rub on the shell that will provide calcium, but in any case the UVB is necessary to metabolize calcium. These bulbs aren't cheap, but they're essential. You can usually get better prices online.
Below are some links to care information that will also help you with the setup and care. Make sure you provide plenty of room, excellent filtration, and a good varied diet in addition to the UVB. Most health issues with turtles are due to lack of space, poor water quality, lack of UVB, or poor diet.