Hi Laura

Not Lavinia here, but wanted to address your jherb question.

IME, jherb over all can help the horse move better.  Don't believe it would directly affect heel soreness caused by trimming issues, ie., under run heel, long toe, lack of  digital cushion development, distal descent, level plane coffin bone, etc.....

Taking them of the jherb is a precaution from "an abundance of caution" ((Dr Kellon).  If you can do it several days before hand that would be where I would go.

You had asked about doasge. Recommend start with 1/2 tsp 2xs per dy, given 20 minutes before feeding.  Check his gums and tongue prior to start.  You want to increase dose until you see obvious pinker color.