Every time I think I'm getting the hang of this, something goes wrong and the number of factors to consider just makes my head spin. I've got a planted 20 gallon tank which has been set up for about 9 months. Lighting is a Finnex planted+ HLC. This tank was primarily a shrimp tank, but I eventually added guppies as well about 3 months ago. 2 months ago, I added some dwarf Sag and narrow Leaf pygmy chain sword to try to get a carpet going in my tank. I added Seachem Flourish tabs in the eco-complete substrate to help them as I read they're root feeders. I started dosing NilocG ThriveS about the same time. It calls for 1 ml/5 gallons 1-3 times a week. I have dosed up to 3 times a week with 3 ml and only one of the pygmy chain swords has started to send out runners. the rest of the carpeting plants are dying back and getting BBA. I stared dosing Excel (slowly at first) 0.5 ml daily for a week then 0.7 ml daily for a week and I'm up to 1 ml daily this week and will eventually work up to the recommended dose for 20 gallons. So far my Jungle Val has not melted and is doing better than most of the other plants. I'm so confused. I don't know why the dwarf Sag and Chain swords are doing so poorly and I'm confused as to why the BBA is taking hold. My nitrates used to always be between 5 and 10, but now every time I check, they're 0. I'm wondering if this is why the plants are struggling and the BBA is taking advantage. I also recently had my 20 year old Whisper 30 HOB begin to fail, so I decided to over-filter and got an Qase Biomaster 250 canister which is loaded with Matrix and has a bag of purigen in it which Seachem says could treat up to 100 gallons. I love how crystal clear my water is, but I'm wondering if this is what's zeroing out my nitrates. I don't know what to do differently. my plants are doing poorly and the BBA seems to be growing fast. Do I fertilize more? reduce my lighting? How do I get my nitrates up? At this point, despite all the research I've done, I've come to the conclusion that I have no idea what I'm doing.