This ficus, unlike the others, is continuing to make many yellow leaves (look at how many have fallen by shaking it). In your opinion for what reason? Many were also small leaves just born (indeed there had been an explosion). Maybe because it's the wall side? What do you say? To @tapla (mid-Michigan, USDA z5b-6a) who will surely tell me to prune I ask: do I prune only sideways or also up and shorten? This ficus was born from a cutting and I have never pruned it.