I'm not surprised that you're having problems. Coco is not soil and should not be treated like soil - it's drain to waste hydroponics. Coco should never be allowed to dry out and should always be fed to run off - this eliminates the possibility of salt build up. Never use plain water because it messes up the cation exchange capacity. If you need to flush for any reason - always use 1/4 strength nutes. I would flush your plants with 1/4 strength nutes pH'd at 6.0 - then start a daily feeding program - always to run off. Daily feeding to run off refreshes the nutes, pulls in fresh oxygen to the roots, and prevents salt build up. I feed my plants daily from the day they sprout and twice a day when in flower.
This plant is 6-1/2 weeks old from sprout for your comparison. Fed every day.
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