Brussels sprouts turning purple

Hello Vero Gee, I recommend to use a pot having enough facilities for aerations and letting percolation rate increases meaning to efficiency for plants to boost physiological process and photosynthesis.

Sali roots are good and soil drains well. It has been raining a lot the last few weeks as well. So you may be right about a deficiency and rain washing out all the nutrients

The other pot which is larger doesn't seem to be impacted as much

Dear Vero Gee, You're quite right Vero Gee 👌 Leaching loss or washing out of nutrients. In such conditions, the lower older leaves supply nutrients to the green younger leaves to sustain the topical growth and the older leaves start drying. This is a common physiological process in plant life. You should remove the dried leaves carefully by trimming. Add some vermicompost together with potassium nitrate inorganic fertilisers for rapid recovery. Hope that it helps!

Very long and brief explanation Sali sir😄😄👏👏👍