Back in February I bought 2 lemon trees and 2 orange trees, to live in my sunny conservatory (South Wales, UK). I repotted them using John Innes n.2 with some added grit and perlite for drainage. I also added a 10cm layer of clay pebbles at the bottom of the pots.I have been feeding them once a week with specific citrus feed, and watering them once a week (occasionally twice a week, when weather was very hot).Despite my efforts, the leaf colour doesn't look right. They are very pale, with visible dark veins. Also, in the last week lots of apparently healthy leaves have been falling. It looks as if someone has cut them off very neatly. Every morning I find 3-4 leaves on the floor.However, all the trees except for one have been producing new leaves and buds. One of them had dozens of oranges at some point, but they all fell off for no apparent reason when they were the size of an olive. Currently, all trees are again full of flowers, but I'm really worried the fruits are going to fall off again.Last week we had exceptionally hot weather, with temperatures reaching 37 degrees C inside the conservatory. Is it possible the extreme heat traumatized the plants (hence the leaf falling)? This would still not explain the pale colour of the leaves...Any suggestions is welcome! Thanks in advance