I'm not sure the Catalina lights will run NO bulbs at true NO power, or at higher power. I think we tested one of them at a local aquatic plant group meeting, and I vaguely recall that a NO bulb definitely does give less PAR than a HO bulb, but I don't remember how much less.
Your problem with the downoi may be CO2, instead of light. You can't rely on a drop checker, when you want to run the CO2 concentration as high as you can without harming the fish. You have to gradually increase the CO2 bubble rate, every 2-3 days or so, watching the fish for problems, and watching to see if the plants grow better. If the plants do grow better, you can again increase the bubble rate slightly and repeat. When the plants seem not to do any better with the last increase in bubble rate, you can drop down to the previous setting and know you are close to the optimum CO2 level for that setup. The drop checker may end up being yellow when you finish.