Dont think this is white spot but can somebody help please?

[orderoutofchaos]

hi
can anybody help with this problem please?
my tank is full of what looks like limescale? the residue is on everything including the inside of the glass and the light on the hood of the tank. it brushes off easily enough but im concerned because its covered the 4 rams i have in the tank in white spots ( i dont think this is white spot as it appeared over night, and theres alot of it etc ). i did add a ph buffer in the night before this outbreak ( its now 6.5) this hasnt affected my black phantom tetras.

apart from the white thing the fish are fine and the water is fine,

can anyone help, its really upsetting me because i dont want the fish to die when its something i could prevent.
thankyou xxxx