Oh gosh, I am so sorry that you lost another one. I thought for sure that the three of them would all make it. You just never know, do you.
You guys have been so dedicated to them and doing everything you possibly can. Like I have read in so many articles, they say is it very hard to raise orphaned kittens, you have to watch out for so many things. Like making sure the temperature is just right, flea anemia, dehydration, just to name a few.

Prayers on the way for the other two.

Rest in Peace little one and enjoy playing on the RB with your other siblings who have gone before you.