I've seen a vid of your flow and it looks fine mate, nice sway to everything, the GSA or GDA has a cycle, about 3 weeks, leave it alone for 3 weeks, clean it off and keep an eye to see if it comes back. If it does see if its as bad as if not might be left over from before. I'd go with low CO2 as it was low for a while after your recent clean up so may be worth cleaning and seeing how or if it comes back.