Need help for identify root problem

Hai all i'm from indonesia, so english not my main language
So i'm sorry if i had bad english

I had problem with my RDWC system
Its not root rot and i dont know what happen

My setting in system
Water Volume 2000 Litres (600 x 200 x 17.5 Cm)
Nutrient 800 - 1000 ppm or around 1.4 - 2.0 EC
Ph 6.0 - 6.4
Temp 28 - 31 celsius

The root is so coarser and thicker than normal root when i started the system 7 month ago. I Always change water every 3- 4 week and add some microbiology like trichoderma and bacillus every week, in 1 - 5th month its okay, but in 6 - 7th it started to more coarse and grow more slow

I give some photo when the root still normal, to compare with current problem

Please give me an answer

All is well friend. Don't worry

Airwalker16 said:

All is well friend. Don't worry

Click to expand...

Did u know what happen? Or maybe becauce lack of dissolved oxygen in water or too much microbiology in water. The main problem is grow become more slower than before

The only issue I see is that you need to swap the lettuces for cannabis plants