Light issues

Don't trust a phone to give you the proper light level unless you put it up against a proper quality light meter.

Raise light

I use an app on my phone that measures LUX. Then, my light manufacturer provided a conversion factor that provides an approximate PPFD value based off LUX. With that PPFD number it is easy to look online at PPFD charts to see how much light to give the plant in each phase of growth and for how many hours a day. Working with PPFD allows you to vary the light's output and height as needed... without guessing at height or where to turn the power dial. You can raise the light higher and at higher output to get more even light distribution in the tent (this might be 50% power at 80cm height). Or you could get the same PPFD at the plant by lowering the light and turning down the power (maybe 25% power at 40cm height) which uses less electricity and generates less heat in the tent. Both could provide the same light intensity but with different outcomes. For example, if I hold my phone at the top of my plant and get 55'000 LUX. I then divide by the conversion factor for my light (65) I get approximately 850 PPFD. That is a good PPFD for a plant in flower on a 12/12 schedule. When the plant first emerges I might want a PPFD around 200. Then 400-500 during veg depending on how tall I want the plant to get. Then in flower I crank it up to about 800 PPFD.

If that happens when you turn it up you may need to lift the light further away from the plants.