Looks a lot like leaf miners. Many useful treatments.

Agree leafminers. But it also appears to have nutrient deficiency based on the interveinal chlorosis and necrotic areas.

Possible causes of chlorosis include poor drainage, damaged roots, compacted roots, high alkalinity, and nutrient deficiencies in the plant. Nutrient deficiencies may occur because there is an insufficient amount in the soil or because the nutrients are unavailable due to a high pH (alkaline soil).

Dave

Are those peat pots?

Thanks all for your help. They are peat pots

That's likely part of the problem causing nutrient issues. I would get them out of those into regular pots if your plant-out is a while away. Or, if conditions allow, get the plants in the ground. They should improve dramatically once that's done. Peel the peat pots off of them first. Or at least slash the pots up really well. Many peat pots don't actually disintegrate well in the ground and end up strangling your plant's roots.

Then you may want to do some reading here of the many discussions about the problems with using peat pots. They may be the cause of some of your nutrient deficiency issues. Please be sure to strip off all the pot before planting.

Dave

Thanks all, I had planned to strip off the pots before planting. They were temporary after the seedling stage. Plant to get into ground tomorrow. Thanks for the advice