Hi. I don't Know much about your story.. Only from what I am reading on this thread. I think you are in the US? I'm not completely sure how health care or caregivers work there so my opinion is based from a Canadian healthcare perspective.
I'm guessing you hire private caregivers for your son? First off.. If these girls are specially trained health care givers, never take on the role of customer/employer with them. That is a pet peeve of many nurses when patients tell us they are our customers so we have to do as they say.
The gist of what I'm hearing is that you have had an ongoing relationship with these girls since you entrust them with the care of your son. The little things like picking up stuff was never expected but you were thankful for because you assumed they were doing it to be kind.. And you reciprocated by doing nice things for them. Generally.. That is how friendships and general courtesies work.
My concern comes when you describe j's behaviour. And especially when she goes on to say you could be a best friend. Because it all sounds very manipulative and crosses the line of professionalism. She knows the boundaries (like not bringing these things up) and yet she does it anyway.
It seems like they are good to your son and of course you don't want to lose that (because employing caregivers that you trust and feel safe with is not easy!) so I would suggest that you use a very soft, kind approach and start setting some boundaries. If they offer to do things beyond what they should be doing, kindly decline. That way you can maintain a professional relationship and lay out your expectations (like getting daily txt updates about your son). And they can never use it against you, or your son!
I have seen many good working relationships from caregivers.. And unfortunately I have also seen bad ones.
As for the situation with L and the hot tub incident... Was she working at the time? Or was it her time off? I understand that you were concerned but, was that within your right? If it is her off time, she really has the right to do whatever she wants (even if you don't like it). As long as her personal life doesn't interfere with her professional life.. (It does sound like some things were questionable). J sounds like she is an instigator. Try not to play into her and she will most likely get bored and find another outlet for drama.
Me:38.. H:33. Two beautiful kids S:6 D:3 M:8.. together for 11. Bomb dropped:10/17/11 Separated:11/07/11