The eye bags someone pointed out in the last thread, potentially from allergies, could also be from dehydration. And the poor kid could wind up with a kidney stone, happened to a friend of mine who didn't drink enough fluids, we thought she was dying the pain was so intense. Could you imagine how painful and terrifying that would be for a toddler?
I think it's incredibly cruel of the Slackers to deny him fluids because they are too lazy to deal with potty training and changing diapers. I agree with what others have said that this is all about their laziness. Them being hoarders and grifters is one thing, but them endangering the health of their child is on a totally different level. They're probably avoiding taking J$ to the doctor because that doctor is going to see a lot of problems (physically, behaviorally, emotionally, pretty much in every way) and they just don't want to deal with it. All they care about is keeping the money train going. Until J$'s health starts causing problems with traveling and filming, they aren't going to do anything about it.