They all got a gentle bath tonight. I used the bathroom sink. Filled it about 2 inches deep with warm water and set them in it. Held them with my right hand (keeping head above water, supporting their weight) and gently rubbed and scrubbed with my left. Once the water turned yellow/brown (oh yeah, it was lovely), I'd pick up the baby and hold it while I drained the sink and refilled it. Most only needed the water changed once, though for two of them I did change it twice. I'd run the shower before we did this, so the bathroom was all warm and steamy (my glasses fogged up) and each one was dried as best we could with a towel before we moved on to the next one. They're currently still hanging out in a crate in the bathroom and I've now scrubbed the (disgusting) floor in their laundry room. At the moment, everyone is basically clean. The little white one actually purred while I was massaging him and then perched on my hand like a little king until it was time to dry him. I like him...he's spunky.

(He then immediately pooped on the towel we were trying to dry him with...he's such a cat.)
Minerva's batch is 5.5 weeks, exactly. I'd guestimate Nala's at 4-4.5 weeks, so maybe 7 to 10 days behind them is all. But the size difference is extraordinary...Minerva's are at least double, maybe triple the size of Nala's biggest ones (and maybe quadruple the size of the Nala's runt). The shelter suggested I see if Minerva would be receptive to some extra babies. I tried one yesterday and she didn't attack it or anything, but she also didn't seem remotely inclined to take care of it (it cried and she walked away, and her own babies are so big that it can't fight its way to a nipple, and the minute her own babies finished, Minerva was done). And being that her babies are so healthy and Nala's not, I didn't want to risk making an otherwise healthy litter ill by prolonged contact.
So, for five minutes anyway, everyone is clean and happy and fed and quiet. We'll see how long it lasts.
Also, I can roughly tell everyone apart now and was able to sex most everyone during their baths.
White one (male)
Black "black" one (looks very dark next to the others, who are more chocolate): female, I think. Only one I'm not sure of.
Thing 1 ---male
Thing 2 ---male (twins in all of their markings)
Runty - female
Big tabby --male (darker, longer hair)
Little tabby--female ("true" black tabby visible in the photos)