It's good to hear your hard work is paying off and you didn't have to run the chiller any colder, at least for now.
Aside from the water-side cleaning and flow balancing I'd guess your results are due to lower airflow; could you hazard a guess what your CFM/Ton is?
Id have to guess
The air flow to be around 350 to 450 per ton.
I don't have a air hood belometer, so I really don't know. One of these days I'll buy one of those hand held vane anemometers, I could figure it with one of those fairly easily.
I'll try and get some info from Trane to see what the cfm is at a give pressure drop across the coil.