What would cause this on my plants?

[Brentweld]

Is it a lack of nutrients? If so which ones

 

[fort384]

What inhabitants do you have in the tank? My first guess here would be something is eating the plants.

If it is a nutrient deficiency I would say potassium... but the damage looks to be too drastic to just be a potassium deficiency.

 

[Brentweld]

I have mystery snails. Trumpet snaiks Olive snails and stiphodon gobys a few shrimp also

 

[boadams87]

Id say snail damage. Potassium isn't that bad.

 

[fort384]

I would agree. Your snails are causing this.

 

[MC1973]

Looks more like plants getting eaten, nutrient deficiency is usually going to show smaller holes.

 

[rkilling1]

Snail damage would be a clean cut, if you will, and happen in a short period of time. A nutrient deficiency would be a hole surrounded by transparent plant matter. It will start small and enlarge over time. Potassium would be the nutrient issue if it's happening to older leaves as this is the common mobile nutrient deficiency.