hydroton white/yellow crust

hey i've got a flood and drain setup and in between waterings when the hydroton pellets dry there are a bunch of pellets on the surface with a mostly white, sometimes yellowish crystalline substance. it dissolves in water no problem and i can't figure out what it is or if it's bad or not. the ph in my system doesn't seem to want to go above 5.0 even when i add ph up. i don't know if this stuff is the cause or not, but i know i'm measuring the ph correctly. any advice would be appreciated.

i think its just the dried up nutes. its all over my drip system but noone can tell me what it is...

just sounds like the salts and shit from the nutes its a good idea to rinse that off with fresh water everyonce in awhile

looks like salts and possibly hard water deposits.