Signs of suspicious spots on substrate

[seashell566]

I have only had my tank running for 5 weeks. My nitrates have been staying at 20ish ppm, while all other parameters look fine. I only have 2 clownfish at this point. Anyone have an idea of what this is?

 

[Reeferjunkie]

Diatoms just a normal phase after cycle

 

[seashell566]

Thank you for the insight

 

[dakoop]

Diatoms