Stinky is always spot on with the adive and troubleshooting, so I would go with stinky's adive on this.
My own expieriences though...my leaves curled up like that one because I was using to many nutes. I stopped and a few days later and they went right back to normal. I didn't have yellowing though...that's why I say go with stinky's advice.
Hope all gets better!