The trailing edges of the fins do tend to stretch over time for most users. They do not stretch due to use, but rather as a result of contact on a surface, especially when warm, like in the car or against the cockpit rails.
This usually doesn't affect performance to any major degree, although if both fins are stretched to one side, you may notice they can be easier to push with one leg vs. the other. On well lubed Drives, the pedals tend to not stay in the down position without help when using them as a daggerboard when sailing.
For your next set, you can keep your fins nice and straight like this with a few precautions.
1. Keep them sleeved until ready to use. Cardboard works great and is well priced as long as you dry the fins before inserting:
2. If carrying them on your boat, position the Drive nose tilted down
or fins up
Once you get in the habit of it, it becomes second nature.