Never mind about the Jelly Tentacles. I just found my first one after like 15 Jelly kills so I was just getting unlucky with the drop rate lol. The game is super awesome btw and I've been really enjoying the battle mechanic!!
Thank you very much!
I've been working on QoL stuff so I'll see if I can hint at how to get a Jelly tentacle better, and maybe edit the drop rates a bit ^^