I found that the biggest problem with that product is that it doesn't kill your plants immedietly, but does harm them for several months (slow growth, weak growth). I believe it contains copper, which can be hard on scaleless fish like plecos and loaches. It will usually kill any shrimp you have, too.
If you need to remove the copper from your tank, you can use PolyFilter to remove it (carbon doesn't remove copper).
If you decide to do a blackout again, you need to do it for at least 4 days, with a water change before and after, and absolutely no peeking, no lights and no feeding during the blackout.
Green water is often caused by ammonia in the water, even though it may not be detectable by a hobbyist test kit. As your tank is only about 6 or 7 weeks old, it's very possible you still haven't fully cycled.