Likely fine.
In a regular freezer I would try to store them so that they have insulating mass around them - freeze/thaw cycles can cause any moisture in the vials to repeatedly crystallize and potentially damage peptides. I would not trust pharma lyophilized stuff to be perfectly dry, much less grey market. But if you use them in the short to medium term, any damaged peptides are likely to be negligible in overall quantity.
If you're storing multiple years worth because you're stocking up, it might be time to think about something that goes colder. I went for the middle ground option and got a freezer that goes to -40F, but a decent amount of people have opted for used vaccine freezers that go down to -80. It'll outlive you in one of those.