NOID Den
 

I posted earlier about the leaves curving significantly but now several of the leaves all are turning yellow at once and some are getting black spots. What should I do? Whats wrong with it?

Can you post pic of the whole plant?
The first two pics don't look alarming - 1st pic could likely be just the leaf is on it's way out, but can't say for sure - is it on older growth?
2nd pic looks like could be scarring from some sort of damage to leaf, again I can't be sure.
The dark area on the 3rd pic could be cause for concern.

I think a pic of the whole plant could be helpful, as well as your growing conditions, etc

Hopefully with some more information as well as an overall picture of the plant some more knowledgable members will have some opinions and advice for you :)