This resembles cold damage. Did the plants experience an overnight frost in recent weeks? Peas are best in cool conditions, but can still be injured in very low temperatures. Heat spells can also stress them, though would likely only cause similar-looking damage if the plants were too dry and needed water.

Since the upper/younger foliage looks fine, damage to older leaves from environmental conditions will be outgrown without any intervention needed. Nothing can heal injured leaves, but the plants may drop those damaged leaves at some point as more new growth emerges.

Miri

Thank you so much!

You're welcome!