Cherry head tortoise shell rot?

[blizzard-king]

In November I received my "well started baby" cherry head tortoise (I suspect he was about 6 months old then and about 9-10 months now). Over the past month I've noticed some white rough spots on the bottom his shell.
February:
March:

The spots are somewhat soft (I can scratch them with my fingernail) and seem to be growing slowly. I've been doing research, and from what I can tell this is a bacterial/fungal infection known as shell rot, which is caused by too much moisture. Early on (December and part of January) I had trouble getting the humidity right, and ended up with water pooling in the bottom of the terrarium. I've since fixed the humidity issue, and I'm trying to figure out how best to treat my tortoise's shell. One common treatment I've heard of is to use betadine once (or maybe twice), and then use Chlorhexidine (brand name Nolvesan, apparently this is a disinfectant). Does this sound like a good approach? I found some instructions detailing the initial application of betadine, but I'm not sure when/how I should be applying the chlorhexidine.

I'm new to tortoises and reptiles in general, so any advice and more specific instructions would be very welcome.

 

[wellington]

The top layer of their substrate needs to be dry and stay dry. They do need high humidity but because they are so prone to shell rot the top layer needs to remain dry. To do this pour warm water into the corners and let it seep through and dampen the bottom layers
For the white spots put some over the counter antifungal cream on them. Like what you would buy for athletes foot. Put it daily until cleared up

 

[ZEROPILOT]

Get yourself some ATHLETES FOOT CREAM.
I actually get mine from the DOLLAR STORE. It doesnt need to be fancier or more expensive.
Smear some on the areas. Repeat in a few days. Keep it up for a week to 10 days. And re check.
Fungal issues can be common with Redfoot. Luckily, it's also very easy to cure. Especially if caught easily. And it seems that you have.
The fungus will die. But the areas will be scarred for a very long time. So don't associate the way it look with the fungus still being active. It may not be.
When the spots are no longer soft, but hard, the fungus is going away.
I have in the past used a credit card or wooden stick to remove some of the soft area. But I personally do not use antibiotics. Not on simple shell fungus.

 

[blizzard-king]

Thank you both so much for your advice, I'll be starting treatment today.