Glad to hear about your Molly. I recently had a Platy recover from the brink of death, it's a good feeling. 
On the other hand, my hamster died shortly after 
About your KH - it's higher than I would like in my tank. Is your pH low enough, according to your target? The higher the KH is, the harder it is to lower your pH. The good thing is that it won't swing as much. From personal experience, I once had high KH water, I think it was around 15, and the plants pretty much withered away, not one of them was doing well. And I was dosing NPK and traces, and CO2 injection as usual. So I'm blaming it on the water, and would never want to deal with such hard water again. You can just lower it by doing water changes, so it's not a problem for you. I'd keep it between 4 and 8. Look into using crushed coral for less maintenance.
On the other hand, my hamster died shortly after About your KH - it's higher than I would like in my tank. Is your pH low enough, according to your target? The higher the KH is, the harder it is to lower your pH. The good thing is that it won't swing as much. From personal experience, I once had high KH water, I think it was around 15, and the plants pretty much withered away, not one of them was doing well. And I was dosing NPK and traces, and CO2 injection as usual. So I'm blaming it on the water, and would never want to deal with such hard water again. You can just lower it by doing water changes, so it's not a problem for you. I'd keep it between 4 and 8. Look into using crushed coral for less maintenance.
