Awwww...I'm sorry to hear that, gal. That's how the one I lost acted the last couple of days before it passed. I tried feeding it separately too, but to no avail. It just stopped eating, and when they are so small, it doesn't take long for them to wither away when that happens.
Keep trying to help it, of course, but if it passes, know that it's not your fault. The other toads are doing great in the same conditions, so obviously your care is good.