I live in Melbourne Australia. It is the middle of Summer. Day temperatures are in the mid 20's (celcius) and the evening temperatures around the mid teens. I generally give my Lemon tree a good watering a couple of times per week and I have some pea straw compost around the base. I have just given the tree its bi-annual feed of Lemon tree fertilizer. There are quite a number of Yellow leaves on it at present. Should I be douing anything different?