My plants hit the wall at 6.5 hours of light a day, depending on what plants you have you may be better off shading the tank and leaving the lighting period at more like 8 hours a day. Bit of window screen or raise the light will reduce the intensity of your new light.
My GW was related to no nitrate with lots of CO2 and light the first epic bout and the rest of my episodes were after disturbing the tank which likely released some ammonia and my filter wasn't up to the task. I could get rid of the GW by allowing the floaters and stems to build up on the surface to dim the light but until I got much better bio filtration it always returned.
You might prune any dying leaves, vacuum the substrate to get debris off the surface and rinse out the filter media too. A long established tank has more organic matter than it really needs, take some out.