What is this white stuff?

[nzafi]

So I have been having this white build up on the powerhead, heater suction cups and rubber part of the filter. Looks like it is only happening on the rubber pieces in my tank. Water parameters are perfect. 75 gal, 1 rhom, 50% weekly water changes, running fx5

No idea what this is, I have had it for months and months. I clean it and it just comes back. Tried to do my best with the pics.

Any thoughts?

 

[Gill Blue]

can't tell from the pics, but I'd guess it's oxidation of the rubber.

 

[xraycer]

I've heard certain water conditioners will cause that on certain rubber materials.