Cyano, Diatom, or Dino

[8675309TT]

Hello, my tank is cycled and has been up for 4 months. This brown stuff appeared as well as dark pebble looking things?

Consensus on if this is Cyano, Diatom, or Dino? How best to treat?

Towards the end of the day (light) makes it worse. I tried 3 day black out and manual removal. No luck. Tried phosguard for two weeks then pulled it out as I read 0 phos is also bad. No luck.
Thanks in advance,
Nick

 

[T-J]

Pic isn't the greatest, but my guess is diatoms. Is it brown and dusty looking? If it's on the rocks, does it blow off?

 

[8675309TT]

Pic isn't the greatest, but my guess is diatoms. Is it brown and dusty looking? If it's on the rocks, does it blow off?

Sorry about the pic. Maybe this is better?