white stuff on bark and yellow leaves!!

[Chiral224]

Hi, I have a couple of 'chids with what looks like mineral deposits on the surface of the media. I've had these guys for a couple weeks and havent used any fertilizer on them, just a bit of superthrive. I ran water through them a few days ago, but its still there and maybe getting worse. Should I maybe use distilled for the next couple waterings or maybe repot them? Both developed a yellow leaf, but I'm not sure if its from that or because its been hot and sunny. All my others have yellow leaves developing too and my catts leaves are getting wrinkled!!! Could it be the superthrive? I had read other post where people use it every watering....

HELP!