Diatoms (a member of the algal class Bacillariophyceae) appear as brown patches, and/or as stringy brown mass. It is especially common in new setups in the first couple of weeks.
Diatoms are readily consumed by micro fauna as the tank matures. In almost all cases, diatoms in planted tanks go away by themselves without further intervention from the aquarist once the tank is fully cycled and biologically mature, regardless of silicate levels which is a commonly cited cause.
"But many papers out there show a link between silicates and diatoms"
Just as many papers show links between phosphates and algae. However, this doesn't prevent us from having totally algae free tanks despite having good amounts of phosphates in the water. Concepts from surveying natural systems do not necessarily transfer directly onto how our tanks work. If you want results, learning from successful tank examples is the best & proven method.
Here are links to further reading on:
1. Understanding water parameters
2. Detailed steps on how to cycle a planted tank