Platies are fin nippers?

[puppyrjjkm]

So I had one of my males in a 29 gal with 6 platies and 3 ADF. About a week later my betta has 3 large chunks out of his tail gone. Is this from the platies? I haven't seen them ever go after my betta. Could this happen from getting his tail stuck on the filter intake? I've had other bettas that have had this happen but just the ends were frayed, not entire "strands" of fin. What do you guys think? Thanks.

[beta novice]

i think its the filter