I am so sorry for your loss. When you are soaking your tortoises do not have the container in the sun as the tortoises can quickly overheat.
Well with no water sources and no soaking, we have found a likely possible cause for your tortoises demise. Dehydration.
I recommend you soak the remaining two daily for at least a couple of weeks to make sure they are good and hydrated. After a couple of weeks of daily soaks, you can taper it down to a couple times a week, but do offer at least a couple of terra cotta saucers sunk into the ground so the rim is near level with the surface.
I use 18 plastic totes from Walmart for this. They only cost about $5 each.
Also keep an eye on the remaining two. Tortoises do not usually get along well in pairs. You might need to separate them. DTs are usually very solitary and don't like competition.
Jay, I am so sorry for your loss. I'm still in grief over mine and I only had her from hatching, 4 years. I hope you got lots of pictures of her with your family. That's one thing I never did. She was kind of like my soulmate. With love to you, Miggy.
If they have burrows that should keep them protected at night and possibly hydrated. When it is really hot, I'll hose Charlie down. It is good to have a shallow pool they can get into by themselves but I don't know much about CDT so maybe that isn't necessary for them.No I have never put them in an enclosure, they usually go to one of there holes during the night. Part of me thinks maybe it wasn't a predator because it was just laying in my planter, they never sleep there at night, always go to cover. It was super hot last week, I'm wondering if it could have gotten too hot and went to the shade and then died? That's what I thought you guys meant as soak, maybe I should be keeping them cool? Not knowing is going to bother me!