From the sound of it, I don't know if there was anything more you could have done to change the outcome. Unfortunately, sometimes they just don't make it no matter how well you provide for them. Again, I'm truly sorry for your loss.
I'm so very sorry to read that the little tortoise didn't make it.
For your own education, if you buy another tortoise in the future, don't use that light. Those coiled shaped bulbs are known to cause eye irritation in young tortoises. It is similar to snow blindness. That isn't what killed the tortoise, but it is what made the eyes swell shut.