Plants Turning Brown?

[zaman]

My plants are turning brown, can anybody tell me why is this from?

 

[d851]

mine are too, can anyone help ?

 

[DarkEntity]

Algae from excessive lighting or over feeding maybe

 

[BigIan]

Copyd from aqua essentials site.

Lack of Magnesium

Leaves become yellow but have green veins; they may also develop brown spots. If your plants are short of magnesium, they will be unable to absorb iron - treat with trace elements.

adding some form of fert should help, seachem flourish is a good brand