The question is pretty straight forward. I make green tea with tea leaves/tea bags it’s not the type in bottles/cans that’s just tea flavor and lots of sugar. I just put a spoonful of powdered lemonade mix in and put it all over ice.
First, it’s good that you’re using actual loose-leaf tea or tea bags–you are right that this is much healthier than bottled or instant iced teas.
There is some evidence that adding lemon or citrus juice to tea may actually enhance the health benefits, but this is mainly because it contains vitamin C, which is an antioxidant, and may exert some synergy with the antioxidants in the tea. If you use powdered lemonade, it may not help as much because it probably doesn’t have as much natural food value. But it’s certainly not going to harm anything (beyond the added sugar, too much sugar is not good for you, but you know that).