A few thoughts for you:
First off, try to avoid using p values as a 'cliff' indicating 'signficance' but more as a measure of probability of getting a test statistic at least as large due solely to chance. Additionally, what do your eyes tell you about group means when looking at the Fit Y by X scatter plot? And most importantly can domain expertise help inform your ultimate decision? What are the risks (practical not statistical) for making a wrong decision regarding groups? These should help guide your ultimate decision AT least as much as a p value.
Lastly, if you are bound and determined to use something that produces p values or their brethren in a multiple comparison mode, maybe take a look at the nonparametric multiple comparison tests? These are offered as a hot spot option from the Fit Y by X platform report under Nonparametric -> Nonparametric multiple comparisons.