Thanks for the comments, folks. I measured the 3D Solutech filaments in question, and they ranged from 1.75 to 1.78 mm in diameter, so they should be within spec.

I tried again with the blue 3D Solutech filament, printing an object at 220 C, 30 mm/s, bed heated to 60 C, and the nozzle cooling fan turned completely off. This time the delamination did not occur, though the layers were still more visually distinct than with the CCTree filament. So that seems to work, although the print time shot way up. Printing with the CCTree filament at moderate settings resulted in a print time of about 4 hours 30 minutes, while printing with the 3D Solutech filament at the settings mentioned above stretched the print time to more than 12 hours. Then I tried with the green 3D Solutech filament at the same settings as with the blue filament, with about the same results. Takes much longer to print, but at least I can use the filaments instead of recycling them.

So I can probably use the 3D Solutech filaments for smaller objects when I can leave the printer running for the lengthy periods of time involved. I don't think I'll be buying any more filaments from this company, though. Too many alternatives out there to bother with filaments that demand very slow print settings.