Suspected nitrogen toxicity?

Electrical conductivity (EC) measures the concentration of dissolved salts or ions in a solution, such as a nutrient solution used in hydroponics or soil water. A higher EC means a higher concentration of dissolved salts, which increases the osmotic potential of the solution. Osmotic potential affects water movement; high EC increases osmotic potential, causing water to move away from the plant roots, potentially leading to water stress, even if water is available. Plants struggle to absorb water from a solution with high osmotic potential, leading to dehydration and wilting. If EC is too high, it can be adjusted by diluting the nutrient solution with distilled water, or by flushing the grow medium to remove excess salts.

High ec I'd guess.

Hi, since you know the EC value of the runoff, you must have also measured the pH value, which should be between 5.8 and 6.5. If it's outside this range, it can lead to a nutrient lockout, and then the plant won't take up any nutrients at all, causing the EC value in the soil to rise even more. This creates a downward spiral of worsening conditions. So, measure the pH and adjust if necessary. 2 possibilities are temperature stress: Too high temperatures or extreme fluctuations can cause yellow leaf tips. Light burn: If the plant is too close to strong light sources, the tips can burn. You should set your lights correctly; use the app Photone for this and try to maintain these values. PPFD: This value indicates how many photons per second hit an area of one square meter. The optimal PPFD value during the vegetative phase is around 400–600 µmol/m²/s and during the flowering phase at 600–900 µmol/m²/s². DLI: DLI measures the total amount of light a plant receives within 24 hours. For cannabis, the ideal DLI value is between 20–40 mol/m²/day, depending on the growth phase. Also, note the number of hours your light is on and what light spectrum it covers. Try this and keep observing.

Looks more like some Zinc defo... Check your PH

i suspect light stress how far away is your plant from the lights and how much is it turned up if it was nitrogen toxicity the plant would be wayyyyyy darker

doesn't look like nitrogen toxicity to me. ive never seen the yellow tips like that for nitrogen toxicity. but maybe too high of nutrients in general and its nute