Zinnia Problems

hi so I have a garden with zinnias. I used miracle grow soil. The zinnias have grown huge and have bloomed really well. However in the past few weeks a lot of the zinnias have gotten holes in the leaves, the leaves have turned brown and shriveled up, and the stems and main stalks are even turning brown now. I have definitely had an insect problem. Japanese beetles, leaf hoppers, and I had a lead footed nymph problem but they are gone now. I still notice the beetles and leaf hoppers. I've tried raid home and garden insecticide and garden safe insecticide with pyrethrins in it. I know that these bugs could be the cause, maybe the leaf hoppers are putting a disease in the flowers and that's why they're turning brown? im just concerned because the thick main stalks are now turning brown in some of the flowers. I don't know if it's a nutritional problem either. I feed the flowers regularly and the miracle grow has plenty of nitrogen in it so I doubt that's the problem. my second problem is my zinnias have seemed to have stop blooming after a great bloom earlier in the summer. I have just learned about the deadheading process and hopefully the deadheading and pruning helps. The fertilizer I use has a lot of phosphorus in it so I don't think it's a phosphorus deficiency. its just weird because now some stems are growing with beautiful healthy leaves with no buds on the ends at all. any suggestions are greatly appreciated thanks so much!

I have grown zinnia here in Hillsborough with no problem in just our clay soil amended over the years. I am wondering if you. are treating them too well with fertilization. After the big bloom and dead heading the blooms definitely come slower... Zinnia are annuals here and I don't have any luck with coming back from seed ....I just plant new each year I want to have them. They take a beating and deer don't touch here and so are a real favorite. Your zinnia sound like my new witch hazel -- Japanese beetles culprit

for some reason my pictures are uploading but when I press send they are not posting. it says it posted but they're not showing up I'm sorry

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Alternaria Leaf Spot or rust?

hmm possibly alternari. however I looked it up and it apparently starts out with black spot that I never noticed. definitely a possibility tho. definitely not rust

I saw some tan in the photos -- made me think it could be it also.