I just fixed the psych chart for Rhino 6:
You can find a working version of the sample file here:
Psychrometric_Chart_Part_2_FIXED.gh (550.8 KB)
It seems a lot of this had to do with Rhino 6 returning the results of trimming/splitting operations in a different order than it had done in Rhino 5, which is something that I should check for anyway.
Thanks again for reporting this!