The Order of the Mutant archetype of the Blood Hunter class has the ability to use mutagens to increase ability scores.
The rule for using mutagens reads in part:
As a bonus action you can consume a single mutagen, and the effects and side effects last until you finish a short or long rest, unless otherwise specified. While one or more mutagens are affecting you, you can use an action to focus and flush the toxins from your system, ending the effects and side effects of all mutagens.
So a Blood Hunter can clearly have more than one mutagen in effect at the same time, but could the Blood Hunter have the same mutagen in effect simultaneously?
Specifically, could a Blood Hunter use two instances of the Potency mutagen to increase her strength score to 26? I'm not sure if the rules for combining spells applies since the ability isn't a spell (or even described as being magic).