on my plants, bacopa carolina most of all, the older leaves are turning brown. it looks like they have a covering on them cause when i wipe them it comes off. my light is 2.66 watts per gallon, and im following the dosing calculator on this forum. the problem could be my diy co2. it seems to be on and off and i cant get it to work right i guess. but anyway, would this cause algae? how can i fix this problem??