I know how you feel.....I'm the same way. I feel awful if I lose any of my Guineas, but the keets are especially bad for me to lose.....maybe cuz they are so cute and sweet at that age. This is just one more reason why I try not to incubate my own eggs and not do the whole brooder thing. I let my hens hatch their own eggs whenever possible and I find I don't get so attatched as I don't have as much direct interaction with them and they are more wild. I last incubated and hatched my own keets three years ago. I had one keet that had a splayed leg. I tried splinting it, but after a few days it died. The next day, I had a second one die (it had a matted poopy butt and when I cleaned it up with a warm rag, it had a seizure and died). I felt terrible and thought, "I'm not cut out to do this....I'm too sensitive (a big baby, really)!" Anyway, since then, I try to avoid much that would get me more attatched than I already am. If you have adults, or when you get adults, you might consider letting them hatch and raise their own, if possible. My adults do a great job and, although I do lose a few occasionally, it's a little easier to handle emotionally!
I hope the rest of your keets do ok!