Negative on the compost with your little jabs. The original "dirt" was probably good enough, given you added your iron and sulfur/soil acidifier. Potting soil= Bad times (usually). Give them a nice peat based mix (Pro Mix Bx) and add a bit of iron and a pinch of sulfur/soil acidifier and call it a day. Get them out of direct sun too. Jaboticaba don't mind a bit o' shade. Hope it recovers. Chris