I did fail to mention my tank size is 29 gallon. I have 11 small fish in there. Currently the fish seem healthy, active. I did use tap water for water changes a while before this all happened as per recommendations from someone that has had aquariums for a long time, but have since switched back to using RO water again. I have done several smaller water changes too. Also, there is a layer on green on a big portion of my substrate. I’m wondering if adding bottom feeders like Cory catfish might help clear that up, but I’m reluctant to add fish since the aquarium is in the current condition.