Over watering is a problem, for me at least. I’m an Aquarius, so…anyway jacaranda don’t like to stay wet. They are a bit forgiving, but I think with all that akadama your soil stays pretty moist/wet. I have to force (lol) myself to give a drying cycle to this tree. Soil should be allowed to dry between watering. It’s what I read months ago when I first got a jacaranda and it’s been growing very vigorously. As far as feeding, a tiny pinch of fertilizer will suffice. 10 10 10 would be perfect, but I doubt that’s a solid fertilizer. Solid slowly melts away and feeds over time. Liquids are more immediate, but not. Most of it goes out the bottom of the pot, wasted. (IMO) also I see negative effects from liquids not solids. If and/or when I use a liquid it’s a 3 3 3, anything else seems to effect it adversely. I’ve been using an 18 4 10 and seems to work great. I don’t use a scoop, I just use fingers and add a pinch here and there. Over fertilizing causes reverse osmosis and will drive nutrients out of your tree. Most call it burn, but it’s way more of a mechanism than a chemical burn. Seedlings really need to be left alone for a very long time! Yours looks good, but I fear you’re fussing over it too much. I know it’s in the nature of bonsai to want to do it, but that’s the patience of the art. It’s taken me a long time and many trees to gain this wisdom, though I still have to fight my urges to water, fuss, and feed! LoL