Under watering + low RH are your issues. For the low RH use a mist maker, an humidifier or put a bowl with water in it like that the heat will make it evaporate ( not the most efficient ). For the under watering well water a bit more , from what I can see the soil is dry so the roots can't have access to the nutrients , the water will make the nutrients available and get rid of the deficiencies on the future leaves.