if you are getting coloration early, it could definitely be the recent intensity increase. It could just be heat too, i believe? Pollination can cause a stigma to brown.
If the increase is still within a healthy range for the hours you run your lamp per day, the plant will acclimate, but if it was a drastic change it may take a moment. Check a DLI chart, light umol/s specs and consider relevant factors. Can eliminate possibility of too much light, unless near that break-even grey area. No added CO2 - ~800-900ppfd (umol/s per m^2)