My banana tree seems to be slowly dying

When I first got it in september it had 6 or 7 healthy looking leaves, now its down to 2 or 3 yellowing leaves.
I've been treating it for spider mites by spraying it with water with a tiny bit of soap. Also, I tried adding coffee grounds to the soil per my dad's suggestion. I don't know if I may be over/under watering it? It has been looking sick for a while, but I left it over thanksgiving (monday to sunday) and it seemed worse when I got back, so I gave it lots of water. The soil seems pretty sad, and when I went to take pictures I realized I could just pull the plant out of the pot with no problem. That's when I discovered the yellow mold(?) and a pretty large grub thing (he was about the size of my little finger nail). I had difficulties photographing them. this mold is actually a pretty bright yellow color, and the bug was just showing up as a spot, so no picture of him. Maybe the bug is normal, but it looked pretty scary to me (haha).

So yeah, this is alot of questions, but on the bright side, a pup sprouted around october and seems to be doing fine. To me, this suggests its not the soil because the pup seems happy, but I really have no idea.
that was a lot of info, so to summarize:
--yellowing, rapidly dying leaves.
--yellow mold on soil.
--spider mites.
possible causes?
--watering difficulties?
--spraying for spider mites?
--that wierd creepy bug?
--nutrients?
--something I have never heard of?
Any help would be greatly appreciated!! Thanks!
