The resistance drop may be just the difference between measuring the carto dry and then wet with e-liquid. I get that with Vivi Novas all the time: a swing of 0.2 to 0.4 ohms from dry to wet. I've never measured cartos on my Lavatube or Vamo.
There are more important questions: 1) Are you getting good vapor, throat-hit and flavor? or 2) Are you getting a burnt taste?
If you answered "yes" to 1), then that resistance drop of about 7% is insignificant. If you answered "yes" to 2), your hole(s) may be too small for sufficient e-liquid feed into the carto.