hi bro, similar to iPhone airpods also have optimised charging feature. based on which bud you are using, battery draining will happen gradually and stops charging after 80%. this cannot be manually controlled.
I hope you do have applecare+ to protect airpods from any manfuacturer defect or user damages for 2 years total. if not do get it right away bro.
Continue using the airpods for few more months and in this 2 years you can claim warranty anytime as manufacturer issue if any such battery related issue occurs.
But right now its not a problem dont worry.