Brown leaf tips

I’m growing Bruce Banner auto hydroponically. Two plants that are about 10 days apart timewise. The older plant is in week five and is 24” tall. Getting 18 hours of light 18” above plant top. 1000watt led light. pH is 6.2, TDS1400ppm. Her leaf tips are turning brown and have a slight bit of curl at the very tip.

should I be concerned?

Could be heat stress, and maybe too much salt build up. Maybe drop your TDS to between 800-1200. You can adjust by adding more water. Have you checked your EC? Also what is your RH?

Looks like minor nitrogen toxicity as your plants are moving into flower, back off the N and get that PK going for flower. Keep an eye on it but I would recommend a flush before flower if necessary.