Hey Nic,
I have been
gardening only in containers for about 10 years because the ground where I live is not really suitable for anything other than desert plants.
My first question is what are you using for soil? The health of your plants starts with healthy soil.
When I first started I was using different variations on the self-watering containers that I made from pairs of 5-gallon buckets and modified plastic storage bins. I bought a high quality OMRI certified potting soil by Kelloggs and amended it with
compost, blood meal, bone meal, coconut quoir, and vermiculite. I have never used any chemical fertilizers or amendments.
I have since expanded my containers and done away with the self-watering types and just use either resin pots or glazed ceramics.
I get that browning on my strawberries, and it isn't from calcium deficiency. I know this because I have the hardest
water in the world! Usually, my strawberries don't turn brown leaves until the second year though. Yours look pretty young. Are they getting full sun? Strawberries like a lot of sunshine.
Some of your plants look like they have some pest problems. Are you seeing any strands of white stuff on the underside of leaves and leaf stems? Those are aphids. Some neem oil or just soapy water in a spray bottle will take care of those until the green lace-wings or ladybugs move in.