Fungus on phal leaves

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I have had a fungal problem on several of my orchids for a few months now. The thin- leaved orchids such as oncidiums seem to be easily controlled using an fungicide, but the thicker leaved plants (such as phals and pseudobulbs) keep on getting lots of black fungal spots that indent into the leaf. Has anyone had this problem?

I will try to post pictures tomorrow.

Thanks, Cam