Aquarium decoration issues

[Jakesaqua]

I have 2 Venustus cichlids in a 29 gallon tank and I have had them for at least a month and a weird orange/brown growth has started on my decorations and I tried taking them out during my last water change and rinsing them off but it wouldn’t come off and it keeps growing and now some of it has spread to the glass and I can’t find a solution to this problem anywhere. Please respond if you know how I can solve this problem.
I attached an image you can see it on the top of the rock and the root structure.

 

[Autumnsky]

Diatoms. They should eventually go away. The love silicates in the water and grow.

You can use hydrogen peroxide 3% like you would use from the medicine cabinet, and a toothbrush on the decorations. Try 50/50% warm water and H2O2. Scrub off outside of the aquarium and rinse off.

Another option might be additional water changes, less light period and if needed something which removes silicates. I have used PhosGuard by Seachem, there are others.