Phals have a crusty tartar layer on roots

[NewBloom]

Several of my NOID phals have developed an oatmeal or golden crust over parts of the roots. This has been going on a while. it's on areas that are not covered by the medium. Has anyone experienced this?

I've been wracking my brains trying to pin point the cause. I've wondered if it can be a reaction to DynaGro's Pro-Tekt because if the undiluted product falls on a surface, it leaves a white residue. I stopped using it for a while. Still, my other types of orchids don't exhibit the crusty formation on roots and they are grown in the same area and fed the same fertilizer.

Btw, several of the phals have bloomed and put out new leaves.