Hi there I am new to growing herbs so bear with me, I am growing mine in pots in an airy environment protected from rain & wind , I have been watering my thyme & lemon thyme daily but noticed today they are both going very dark brown/black at the base of the plants. I noticed the soil was very wet so I have taken them out of it and put them in dry soil am I to late to save them & better off binning them and starting again??
I can't tell if they can be saved without pictures (and possibly not even then). One of the things that could have happened to them is root rot. So you need to slide the root ball out of the pot it is in. Check to see if it is pot bound (i.e. roots going around the outside of the ball in circles). Then gently wash some of the soil off and check the roots. They should be light colored and firm. If they are brown/black, mushy, or smell bad, they are rotted. If there are some that are healthy, prune out all the rotten ones. Loosen any that have been going around the outside, so that all the roots are hanging down. Then repot in potting soil made for cactus/succulents which will be much less moisture retentive.
Thyme is a desert plant. You have been killing it with kindness. Watering daily is way too much (if you have been wetting it thoroughly each time). What you want to do is water it until all the soil is moistened and water is running out the drain holes. Let it drain and then DON"T WATER AGAIN until the top couple inches of the soil are dry. Depending on your soil type, how much sun it gets, etc., that might be once a week or it might be every other week. I have had house plants I watered once a month.
If you replant it, put it in a wide terra cotta pot. It breathes so it dries faster and use a light mix. A cactus mix with a couple of handfuls of vermicast or peat moss helps. I water almost every day too. It is easier for me to modify the conditions to account for my watering than to modify my habits. I do keep my succulent and low water plants together and in full sun out of reach of the sprinklers. And while I water almost every day or two. I try to go over those areas quicker than usual so they don't get a soak. I can't keep thyme a live for a long time either. I have to keep ground layering and dividing. The centers eventually get too woody to come back and so I have to have a few pots around to have constant supply. Trimming herbs often helps to keep them bushier longer.
Happy gardening in Hawaii. Gardens are where people grow.