For "handmethehammer" Citrus like 60% RH. Your problem is the same, too high a VPD. Citrus can only move so much water from the roots. Beyond this they require humidity to cool the leaves and keep the transpiration rate low. Indoors flowers, fruit, and leaves will all fall if the RELATIVE HUMIDITY is too low. First thing you need to do is heat the roots. I grow in galvanized pails and wrap a germination pad around the pail. Don't use tap water because it has chlorine and fluorine. Use RO water. It is slightly acidic. Provide lots of airflow. Use a humidifier, mist, and use a humidity tray to increase the humidity as well. When the leaf and root temperature are about 30F apart you will get WLD. South facing window when the sun is directly facing the plant will heat the leaves easily to 95F without air flow. Raise root temperature to 85F, cool the leaves with a fan, fertilize the roots and feed the leaves. The flowers need an even higher amount of RH. You need to mist the plant. Oh and I almost forgot the most important tip. When you water heat the water up to 85F. If you are using tap water at room temperature you are shocking the plant which causes leaf drop. More humidity, more misting, humidity tray, humidifier, air-flow, no tap water, heated roots, fertilize both top and bottom.
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