first pic looks like some type of insect damage ie.spider mite, thrip etc... second pic looks like a combination of the inect damage and calcium deficiency. third pic those big brown spots look like bacterial leaf spot, or what dinosaur bone suggested... "septoria" disease.
here's what i would do, first make sure your ph is in check. 2nd remove all/most of the affected leaves. 3rd treat with and organic fungicide ie. copper or patassium bicabonate or as a last resort some neem oil. 4th about the possible insect problem, when you apply the fungicide make sure to drench the entire plant undersides of leaves stalk stems and all! i reccomend this because you may be able to drown any possible insects that may be on the plant. if the white speckling on the leaves (insect damage) persist you are gonna want to apply some sort of insectcide.
thats about all i can suggest, that and dont panic, calm down, relax and watch the plant to get an understanding of whats happening. these plants are very resiliant, its not gonna die overnight so chill and try to learn what you can.
also if you want to see the pics the article is from ICmag in the outdoors forum, shouldnt be hard to find.
peace
