The yellowing of the bottom leaves is fine, those leaves are known as "sucker leaves." As far as the rest of the leaves, theres a few things that could be happening, if they are turning yellow and curling, my guess would be, yes, a deficiency of some sort, but i would lean more along the lines of a nitrogen deficiency. Nitrogen is the main component in a plant that essentially turns them green. If nitrogen can be ruled out, i would say humidity problem, if the plant is not getting proper moisture, then thats a given its going to turn yellow and crumble. Spray the leaves down with a spritzer bottle if you can, but make sure not to over-do it. Thats really all i can think of off the top of my head for the leaves, but as far as the nutes, my personal favorite is bat guano. Bat guano can be bought at most agricultural stores, and its a slow releasing nute, which greatly reduces the chance of a nute burn. And now that i think of it, if your leaves are turning yellow and if you've applied some type of nute to it previously, you could have possibly burned the roots, which would cause a discoloration of the leaves and probably death.
Thats my 2 cents on this one, i hope it helps out, if your still having issues then let me know and send some pictures and ill see if i can help anymore