Part of the problem is that your tank is relatively new.
Your lack of filtration also likely lends itself to some problems. Are you able to get a better canister filter? Part of it looks like it could be a build up of random mulm-type gunk.
What are your specific water parameters?
Why are you changing your water three times per week?
Sounds like you've still got quite a bit of lighting. Do you have access to PAR data for the fixture so you can determine your light level?
Also should note that bubbles per second isn't an effective way to determine CO2 concentrations. Are you using drop checkers in your tank to help estimate the concentration? Why aren't you providing fertilization if you've got tons of lighting and are using CO2?
Finnex PX-360 canister filter
Aquatek Mini on a 20oz CO2 tank (3 BPS)
BuildMyLED 36" fixture dimmed all the way down and running for 7 hours
25% water change 3x week
Water parameters are spot on
1 Month old