10 year old+ lemon appears healthy but some foliage showing signs of distress. Tree spends summers outdoors and winters inside under grow lights. Thanks for the help.
Eastern PA

Photo number 2, 4 and 7 are showing a magnesium deficiency. You can correct it by applying Epsom Salts (Magnesium Sulfate). Apply 1 tablespoon in a gallon of WARM water evenly to the tree's root system. Apply this solution every week to 10 days until condition improves. Be sure to use warm water, as Epsom salts does not dissolve very well in cool/cold water. The other leaves shown look fine. - Phil Robertson - good man