m0useanswered grow question 2 years ago hard to fully say. If they where healthy not to long ago it might be something changing drastically in the medium like PH or lights are to close or roots are drowning.
If any liquid have been left on the leaves when the lights are on it can also affect them like that.
Lower leaves yellowing is normal when the plat grows out. just means its getting hungry and its a sign to boost feeding regime.
I'm not seeing any fertilizer in your setup and it might be time for some. The root booster is nice but does not contain enough essential elements "NPK" to sustain life, it is a supplement/booster vs a fertilizer
Good Luck!