What's doing this?
overcrowding? They seem to be clumped together pretty tight. Maybe thin out some of the weaker plants and allow the others a little more room?
Also a bit of sun scorch? Maybe they were sprinkled on their tops during a sunny part of the day?
They may be overcrowded, but that shouldn't bother them right now... the soil is brand new, there's lots of yummy soil amendments and compost, and they aren't THAT overcrowded really. I've had way more overcrowded beets in the past with no affects.
As for sprinkled... could be... but I haven't watered them - only rain.
Another possibility would be an insect pest -- leaf miner. Several different insect adult lay eggs whose larva then mines in the leaves. Sometimes they look like someone scribbled on the leaf with a silverish marker and sometimes you'll see a whitish transparent blob where they've been. Is there a little black spot near an edge (that would be the larva)?
You can pick off damaged leaves, target the adults before they damage starts or spray before the damage gets too bad. How you choose to address it depends on if you prefer organic solutions. Do you have a local gardening center that can look at a leaf or a savvy friend who gardens?
Jules - That's exactly what I should do.. .but I haven't got around to it yet...
Instead yesterday we spent taking down part of a willow tree that fell down in the rain storm. Had big potential to hit either - trees, fences, neighbour's house, other neighbour's garage. By pure luck, it fell on one piece of an old fence, and missed our sunroom, the nieghbour's garage, and the other neighbour's garage. Perfect! We should probably take the other half out too... since it's leaning a litttle towards the house. DH's back is a little sore today, though, so maybe after it recovers. The other half of the tree would be a lot more difficult since it's over the house and we don't want to wreck our roof!
In the meantime, the garden seems to be recovering from our massive hail storm.
On teh other hand I found SLUGS this morning! AHHHHH! I can deal with almost everything else, but slugs just repulse me!
I'm with you on the slugs! One of my kids told me that you can put copper around your garden/plant and the slugs won't cross it. So far it's worked this year. I even got to harvest lettuce.
copper works, as does a cup of beer. (except after they drown in it, you still have to deal with them!)
Putting salt on them makes them bubble and vanish. Pretty horrible though and salted soil doesn't grow plants well!