What are early signs my plant is getting too much heat?

I have a 630W CMH light fixture it gets REALLY HOT, the light sits about 4 Ft above the plants, the ventalation system is on im not sure how much hot air is being sucked out of my closet. Im a first time grower can anyone tell me early signs my grow room is too hot? My plants are 19 days old and the leafs at the very bottom are getting crispy ..but the top leafs look fine. Please help, thanks! Also, do you guys recommend sun glasses to protect my eyes because the room is fuckin BRIGHT! JESUS, WHATS SOME GOOD NAME BRAND SUN GLASSES OUT THERE?

Twisted and curled leaves

I'm having same issue

Ive just started running a 630wDE CMH after running a 600w HPS. The CMH is not as hot.

But the very first sign is a blistering on the surface of the leaf, followed by a slight curling on the serrated leaf edges.

If the bottom leaves are crispy and the tops are fine then whatever problem you have is not heat related.

Yes, you should wear proper grow glasses.

I use these, they work nicely.

https://www.thinkcrucial.com/products/2-grow-room-greenhouse-light-glasses?variant=42530795150&gclid=Cj0KCQjwtMvlBRDmARIsAEoQ8zSAm8