curling leaves means??

ive had two indoor plants since april 7 and they look like they are doing great. the only issue im having is that a few of the leaves are curling. they are still perfectly green. and on one plant the very bottom leaf has two tiny brown spots, this means ?? and i just put them on 12 12. nutes every two weeks and distilled water everyday cause it evaporates quick. i'll take any advice, thank you
 

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