That's why I never use any commercial mixes containing "enough nutrients for 3 or more months" . They put granules of slow release fertilizer into the mix( slow release fert is bad for weed) which cause burn if the roots get to it.
I make my own mix being "burned" many times by commercial mixes, sometimes the most expensive ones are the worst ones. Number 1 junk mix is Miracle Grow.
Canadian peat moss is the best proven over the years base to build quality mix from ground up. It is cheap, available, has anti fungal properties. Just needs little PH up adjustment.
I was never disappointed using it in mine 30 years broad gardening experience.