Hope it's ok to ask for help here... We've had this for a couple of years now, and apart from an aphid infestation a long time ago, it's been pretty good. But recently it's been looking very sad. Leaves are pale and veined, and drop easily. It's still (trying to) flower but definitely not right.

It's in a sunny position, and watered with rain water / general bonsai food. I had read it might be nitrogen deficiency, but the feed definitely contains that.

Any advice on what else we can do to improve things?