White crystalline residue powder from nutes

I have one tray that is in a new area and the grow tray has a white powder on it and it is also on the base of the plant. Never had this prob before. I have one tray with an aquarium thermometer heating the solution because it is outside of normal grow area. It has a white crystalline deposit all over it. NO mites...I know those well. ph is good, plants look good with slight leaf tip curl on a couple and are four weeks old...any ideas? Looks almost like calcium deposits....using rock wool and root booster...roots look good, no fungus....

due to the salts in the nute solution.

best to feed with nutes twice - then just plain water for every third watering/feeding.

this allows the salts to be flushed out of the container bottom.

just wash deposit out of grow tray, waould n't mess with the plants if i were you, once they get a few waterings of just water they will sort themselves out. salts at base of the plant will drain into tray.

its probably from the water heater making water evap. But its just salt build up. Just flush often