The watering frequency may be the issue.
Hope this info helps with your coco grow.
The is a quote from ledrf.
1. Coco holds 30% oxygen when fully saturated.
2. If you let coco dry out, you will get lower yields and most likely nutrient issues because when the coco dries out, it leaves dry spots, where the roots dry up and die. That causes issues.
3. When you water every day or twice a day or ever three times a day, you are replacing all the oxygen the plant used up, thus letting it grow faster. You are also replacing any nutrients the plant used up with fresh nutrients. This is why I water every day with nutrients.
4. You get hydroponic results. Fast growth. Bigger yields.
Don't forget to keep your ph between 5.5-6.0. Most keep it at 5.8
How to water Marijuana growing in coco - YouTube
This thread has great info if you haven't seen it. I dont use the same nutes but I make it work for me.
Ledrf
How I grow in coco Youtube videos and pics
cultivator
How to grow in Coco - Feed schedule
Ledrf and cult have different grow styles but both have great info to share. I use ledrf style but if i was in a grow op id grow like cult as its less waste.
Here is ledrf sponsored website. It has a free grow course. I highly recommend it!
How to grow marijuana free lessons
For seedlings I water every day with a light nute solution but not to runoff. Just a very light splash until they start drying out more and more.