A simple proposal will do the job:
Stop the unprofessional comments or I walk.
Speak to your other bandmates before speaking to the problem child. They may share a similar opinion.
It's amazing how many players believe that going from Thomastik flats to heavy gauge drop tuning rounds won't have much effect on the neck.
I find even switching brands, still the same gauge, will require a truss rod tweak.
Difficult situation now... I like the Spark and Beta MKII in different ways. The Spark is more neutral and organic sounding but the Beta gain and break-up sounds more valve like... sigh! Beta reminded me a lot of the Bearfoot Blueberry.
Apologies, didn't even mention the bass guitars in the original post.
2016 Fender American Standard Jazz Bass installed with DR Pure Blues.
2021 Squier 40th Anniversary Precision Bass installed with Dunlop Flatwounds.