Beetroot lurgy - ideas?

Looks like watering in the sun, as water droplets on leaves act as a mirror that burns them. I think they'll be ok.

I was thinking leaf miner too - anything in the beet family seems a bit prone to it here.

By the time the leaf is damaged and dried to that extent the culprits have usually left the leaf to continue their life-cycle ( ) but in the early stages of attack you can usually see it chomping its way between the upper and lower surfaces of the leaf (and then squish it - it has already spoiled that leaf of course, but it will make you feel better.  )

Their attacks don't usually confine themselves to just the edge of the leaf, as a few of yours appear to be, so if there is no evidence to the contrary sun scorch is also a possibility, as GG has suggested.

Whichever it is, they should recover OK.

Beet leaf miner I would say. No need to blame neighbours watering.

Look on the undersides of the healthy leaves for the tiny white eggs, often in clusters of 3/4. Rub them off before the maggots hatch and burrow into the leaves. There can be 3 or 4 generations in a season. Later on when the plants are bigger you will hardly notice them. When the maggots have finished feeding they drop into the soil and pupate. They overwinter as pupae and the flies hatch out in the Spring to start the cycle again.

There should be no long term harm, it looks worse than it is.

Looks like leaf miner to me too. I've had the same on my swiss chard this year. I picked off the damaged leaves and picked off lots of tiny white eggs on the underside of the other leaves.

I check them every few days and wipe off any eggs, and they're now growing quite happily without any further damage. Phew!!