R.I.P. lucio

[daybr4ke]

First off, before anything else, I'm sorry for your loss. Red Leg is a very deadly disease. It is caused by a bacteria called Aeromonas hydrophila. This bacteria breeds in unclean conditions. Prevention is fairly easy; keeping the water dish clean, keeping good spot cleaning(removing poop and stuff), changing out the substrate(unless it is a bioactive/living vivarium) every 2 weeks or so. A good time frame for keeping the dish clean is to replace the water every day. Every other day at the most. You should remove it and wash it with a frog safe cleaner every 2-3 days, sooner if it gets gets dirty and/or they poop in it. Cleaning the tank after switching the subatrate is also a good idea.
Again, I'm sorry for your loss. Even with good care, it is always possible for things to go wrong. A piece of poo may sit unseen under a leaf or behind a tank decoration.
If you need treatment in the future, it is possible to use fish antibiotics on frogs. I heave heard many uses of Maracyn 2 on Red leg and other bacterial infections. I would say across all my reading there is about a very good chance if caught early(which in some cases may have been irritation or a more mild infection of some sort) to a low chance if caught late. This can be tricky, since irritation to the underbelly can be mistaken for Red Leg. Other infections can have a similar effect, as well. I found it at petclub, while a respectable reptile store had only tetracycline. I figured at the time that whatever they had was the best I was going to get. API T.C. Tetracycline would be my second recommendation. If you CANNOT find Maracyn or get to a vet for prescription antibiotics(not gonna lie, I know nothing about prescription frog medication) then API T.C. Tetracycline may help.
I hope this helps.