I think your issues come from the different mixes of soils and conditioners and all the stuff. Soil is tricky and really tricky if you don't know what's really in it. You can have it tested. Any local college will usually do it also some landscape supply stores and there are online kits. You just get it tested and don't have to tell them what it's for. If you have test results you'll be able to get a real answer. I think switching to pro mix is a good idea for you since you'll have more control and room to play and less issues to start. But I feel like coco might be right up your alley. Only downside of Coco is you have to water everyday but you seem to put enough time into your plants to do that. Best things about it are bigger plants and if something isn't going right you can just wash it right out and go straight back to what was working