It could be overwatering. Make sure that the soil drains well and let the plants dry out between waterings. Watering at night could also cause some of the browning of the leaves if they get wet and stay moist all night. It’s recommended to water Veronicas early in the day to give the foliage a chance to dry before nighttime. If you’ve experienced frequent rain, amend the soil to improve drainage—as well as you can without disturbing the plant.
It could be overwatering. Make sure that the soil drains well and let the plants dry out between waterings. Watering at night could also cause some of the browning of the leaves if they get wet and stay moist all night. It’s recommended to water Veronicas early in the day to give the foliage a chance to dry before nighttime. If you’ve experienced frequent rain, amend the soil to improve drainage—as well as you can without disturbing the plant.