I bought two hanging baskets of dwarf Mandevillas this spring. They were doing fine in the beginning but the leaves have been turning brown starting more than a month ago and barely any flowers. I actually watched the brown leaves issue closely as this happened last year and eventually killed my Mandevillas. At the first sign, I removed all the infected leaves but I knew it's just a matter of time that the plants will die.

I also got two regular Mandevilla vines which my friend gave me about two months ago. She has been growing these for years and I'm afraid they are under the same brown leaves attack in my garden. I tried to remove the infected leaves and spray some fungal/disease control that I got from Home Depot, but not sure it will save the plants. I tried the same thing last year for the dwarf Mandevilla including cutting down all the branches but was in vain.

The hanging baskets are a little bit high so every time I water the leaves they are somewhat likely to be wet. The tall ones are in big containers positioned in the garden against the fence and the sprinkler may touch the leaves too every 3 days. Besides that, weather in Texas has reached triple digit, but I don't think it's a burn issue. The drainage in these contains are fine as far as I'm concerned. The only thing I can think of is I added fertilizers to all of them when I received the plants. Maybe I put too much fertilizers? There's also issues with my pear trees. These are Japanese pear trees that are vulnerable for blight which I have been battling for a couple of years now. I suspect that the brown leaves of my Mandevilla may have something to do with the disease being spread.

Can anyone shed some light on the brown leaves issue for my Mandevilla?

Thanks!