Leaf end tip burn black seeded lettuce

I have some salvanova also but a bit of leaf tip burn showed up. Some where I read to increase air circulation. A small fan has helped with the second crop.

Tip burn is caused by one or more of these problems. Not enough calcium is the most common cause, however low calcium can be caused by low or high pH. Lettuce in particular needs the pH managed between 6.2 and 6.4. That allows optimum nutrient availability. Low calcium may also be because of too weak of nutrients. Black seeded Simpson grows on the lower side of 1.4 to 1.75 EC. The last cause of tip burn is lack of air movement over the lettuce.

Lettuce grows from the inside. All new leaves appear from the center of the plant. As a lettuce plant grows it uses CO2 to form sugars and cell walls. But as a plant grows, photosynthesis converts CO2 to O2 the O2 is pure oxygen and needs to be removed so the leaves can get CO2. This production of O2 creates a microclimate in the middle of the lettuce plant. That microclimate is removed outdoors by wind and temperature changes. Indoors you need a fan to do this.

Your lights aren’t burning them are they?