Is this a fungus? Looks burnt, doesn't grow [Pics]

I've had VFTs for a few years now, and I know about how they get burnt-looking if you rescue one from Lowe's and throw it in the sun, and they always come back making leaves that tolerate the sun. But I have VFTs that look burnt on flower stalks, and one looks burnt on every leaf. They've been outside for months, and other VFTs are doing great.

I'd probably guess sunburn. My plants get this throughout summer unfortunately, as temps rise and humidity drops.