Phalaenopsis with white stringy substance on underside of leaf

[brandiloring]

Hello all,

I have Phalaenopsis orchid that has about a dozen of finger like white protrusions with white chunks on the end of the protrusion on the underside of only ONE leaf. I have 5 orchids total and no other orchid has this on them. My orchids are sharing a large bay window sill space with other orchids and plants. I have moved this orchid with the mystery substance away from the other plants just in case it’s contagious.

I did let some of my orchids spend some time outside this summer. I did not use any spray on them. They have been inside for several weeks now but this hasn’t been there until a few days ago.

Has anyone had this on their orchids and if so what did you do to remove them?