I posted a similar question about small worms in my Calathea a week or two ago. My boyfriend bought it at Home Depot or Lowes. I had the
plant a good 6 mos. or more and it just died this week.
I knew it had problems with fertalizer burning and whiteflies but I didn't realize the worm problem until last week. I tried washing the roots and washing the pot with antibacterial soap and repotting it in a different pot. I also sprayed the roots with Safer pesticide. It's organic and includes worms, many don't.
It appeared the worms ate the roots or something. My roots had lots of small clear gel substances on them. When I looked closely baby worms were inside. I had to carefully go over all the roots and remove them.
The worms may have come from the store or being set outside. The only responder to my inquiry said it could be butterflies that implanted the worm eggs that killed my
plant. But taking care of the problem early should help. This appears to be a relativly new problem with houseplants because I searched high and low for a solution and not many answers were availble on the Web.
Anyway, that's my multiple cents. Good luck.