Mint leaves turning pink??
I recently went on vacation for a couple of months, so I left my beloved peppermint plant with a friend to care for it. When I returned last week, I found that the leaves had half turned a rusty/pink-ish sort of colour and the problem seems to be worsening. Also, it seems to me as though it's growing much more slowly than normal. She hasn't the slightest idea of how this happened. I did notice that she put some tiny orange clay-coloured balls on top of the soil - she says they are charcoal (?) and meant to simply absorb excess water. I'm not sure if they caused the problem.
In any case, if anyone has knowledge about why a mint plant might change colour like this, please tell me! And also would welcome suggestions for how to fix this.
All of the other plant I left with her did brilliantly...
(By the way, this mint has always been an indoor plant)