Storm wrote .'I've lost everything that I tried growing on the balcony so far".
Reading this sentence the very first thought that entered my mind was, the type of medium your trees were growing in.
Organic potting soil and a lot of perlite, it was free draining, no pooling with good watering. I changed it twice over 4 years. Both trees were doing "okay" for the first year, but didn't really put out any new growth, and a lot of spiders seemed to really enjoy webbing the leaves. In the last year, one of the plants developed black-ish leaves, I cut it back a bit, no growth after almost a year, everything dried up. The other one just kind of never put out new growth for 2 years, and then all the branches just dried up. However, there's growth occurring below the graft on the rootstock. I've already removed both, so no pictures.
Once the stay-home is lifted, I'm going to visit a few nurseries and bix-box stores, find a couple nice citrus for potting and a mandarin for the outside ground spot (unless I find a different fruit for it, I like unique things), and am debating whether to use a variation of citrus potting mix with 50% extra inorganics, the 5-1-1 (plus turface fines, so, 5-1-1-1), or the 1-1-1 gritty (which'll get heavy). Fortunately no HLB in my area yet, Plant Depot is pretty close to me and still sells citrus.
Still a few things left to figure out, but, feels like I'm on the right track?