in this case when it is as extreme as that and isolated at the top, it's most likely light/heat stress.
"praying" can be caused by other things, so you have to cross-reference whatever you can... this is beyond normal turgor pressure in the plant. If you continue, you will eventually see some leaf damage. It doesn't always happen over night. Sometimes it can take weeks if only slightly giving too much.
Raising RH can help, but may need to reduce power or raise lights, too.
Read up on Daily Light Integral (wiki). Dropping 2 hours might also fix it, if giving too much "DLI." More is not better with light. How much you can give per day will vary based on light, temp, RH, and atmospheric CO2. A light producing 35-40 DLI at normal hanging distances for modern LED grow lights is a good starting point. You'll still need to observe and react to plant to fine-tune how much light you give per day. DLI tables exist for reference. You don't even have to know the math, but you need to understand the gist of it.
hours, dimmer, distance for light are all options to adjust how much light you provide. Assuming normal hanging distances, better to adjust hours before power, as that will maintain better penetration of light, if more intense over fewer hours. Hanging distance should be about the best coverage of light (geometry), but if you hang it a bit higher while maintaining overall DLI you'll get better penetration while wasting a bit more electricity - more power means more heat too.
