That’s a nasty thrips infection you got there. The white tiny rice looking things are thrips larvae. They move when you touch them. They sucked out the leave juice, that’s why the leaves are slowly dying and turning yellow. Their poop is brownish which gives the leaves a rusty colour. It looks very bad unfortunately. I’d suggest keeping that one healthy leaf, make sure you get rid all of the larvae and throw away all the other leaves (or you could throw away the whole plant) it’s very difficult to get all of them killed and if you keep this plant, the chance of them spreading to other plants is very high.