All the comfrey/borage/nettle teas don't come with a manufacturers' recommended dosage. It's all too easy to overdose one's free fertiliser. Maybe some of us don't really believe how good some of these old natural teas can be, and tend to overdo it. They really can be quite strong if not diluted properly and fed too often, especially with the comfrey on tomatoes.
I plead guilty to overdosing sweet corn sometimes with nettle tea. The plants need water, water, water and they need nitrogen, so I go mad sometimes when they're young.
It's a feel thing that can be quickly understood. If in doubt, once a week, max, fertilser wise.