Strawberry leaf problems

[Aiki BRi]

I am new to growing strawberries and have several in a layered planter, I have just noticed a few leaves with what looks like black splash marks on them almost like someone has splashed ink on them but it appears to be within the leafs surface, the said leaves have also started turning brown and drying up at the edges, does anyone have any ideas what it could be?

[terrier]

Could it be lack of water? I grow a lot of strawb plants in troughs and if I get the watering wrong, they look terrible.One trough I had forgotten to water looked like someone had sprayed it with weed killer but after a good watering, it has perked up.