Light stress or normal

Light stress or normal for week 3 flower? All went well until I flipped. Now it’s got a little burnt on the tips. I don’t think it’s light stress bc none of the leaves are canooed or tips curling up. I use fox farm soil. Ph to 6.5. Last feeding I used tree trunk silica from Humboldts secret. Lights about 20 inches away from top of canopy. The discoloration is on 2 different plants of different strains. I appreciate the help. It’s probably just normal fade but it’s a little early i would think only being week 3. Added a picture from top
 

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