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By regulations most herbicide must dissipate over a period of time, but the damage could be done already by the appearance of your plants.
You can try washing the soil with heavy watering.

A soil test can also be helpful; to know how to help your plants and the only way to really know what amendments your soil needs.

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/how-long-does-weed-killer-last-in-the-soil.htm

Generally, 90 to 120 days is sufficient. Manures naturally contain bacteria such as E. coli and many others that will often harm humans if not composted correctly.

Generally speaking, I would only recommend raw manure if you have absolutely NO underlying health problems, take no medications, and have no other reason to believe that you have a compromised immune system.

If you intend to consume anything grown from this, it is even more important to let it age, as these risks increase dramatically.

Here are some articles that will help:

https://www.gardeningknowhow.com/composting/manures/horse-manure-compost.htm

https://www.gardeningknowhow.com/composting/manures/the-benefits-of-manure-in-your-garden.htm

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/using-fresh-manure-in-gardens.htm

The problem with raw manures will be that there may not be enough of a microbe count in your soil to break it down. This can leave it susceptible to infection, or too many nitrates that may burn the plant. I always recommend well-composted manure.

Some plants can handle it, uncomposted, but you will need to test a small amount beforehand. This will ensure that the plant does not have a negative reaction. Still it is best to use composted manure to rule out all doubt on the subject.

This article will help: https://www.gardeningknowhow.com/composting/manures/the-benefits-of-manure-in-your-garden.htm

First, I would highly advise against uncomposted manure. It can contain deadly pathogens and can burn plants fairly quickly.

Should you choose to use fresh manure, make sure to follow safe use guidelines, which can be found within this article:

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/using-fresh-manure-in-gardens.htm

If you should still choose to use fresh manure, just do a thin top dressing, avoiding the manure touching any of your plants, directly.

That sounded like a lot to me, too, and I found varying recommendations in university extension publications, from 100 pounds per year (per 100 square feet) to 200 pounds per year (per 100 square feet). I believe that is if you are trying to supply most of your nitrogen needs from that application. With that much manure, you have to be careful about not getting too much phosphorous and potassium. Other sources said add a 2 to 3 inch layer around existing plants and work into soil or leave as mulch. That sounds much better than a 4 to 6 inch layer.

I would not add it both fall and spring. All the sources I read said one or the other (once per year).

You wouldn't cover any existing plants with it. You can use it as a mulch and put several inches alongside your plants.

https://wimastergardener.org/article/using-manure-in-the-home-garden/

https://cals.arizona.edu/backyards/sites/cals.arizona.edu.backyards/files/b13fall_pp9-10.pdf

https://www.gardeningknowhow.com/composting/manures/the-benefits-of-manure-in-your-garden.htm

You can, simply, top dress if you would like. I prefer to poke thin holes with a nail to perforate the top of the soil, but this is not completely necessary. It does help to get some of that manure down to the roots, faster, though.

You can mix it, gently, with the mulch or top dress.

Here is an article that will help you with using manure:

https://www.gardeningknowhow.com/composting/manures/the-benefits-of-manure-in-your-garden.htm