charging a lead acid battery bank with a 19v laptop charger
1 - Look, the first thing you need to do is get a cheap DMM. As it stands you have no idea what is actually going on in your batteries, and frankly I'm surprised at how durable lead-acids can be when subjected to the abuse that you are apparently putting them through. Once you have a meter, you can look up "lead-acid charging algorithm" online and learn how to do this right.

2 - Your 48-volt charger was an abortion. Never, ever, use a charger that boils the electrolyte. I suspect that the only reason the PSUs don't cause boiling is that they simply can't produce enough power, while the monster can. And does. Get rid of it, or learn enough electronics to figure out the charging circuit and modify it. You are causing long-term damage to the batteries if you use it.

3 - There is no "intelligent coordination" going on. All of your PSUs are in current limit, and the smaller ones simply don't handle it as well as the larger. The exact hows and whys depend on the circuit design and components/assembly techniques, but it's not a matter of coordination, intelligent or otherwise.