| I have soaped with spearmint (without any problem) but I have not soaped with thyme. Here are some ideas that I would ask for most failures, these may not suit your situation, but here goes: First make sure that the scents are EOs, not FOs. We don't know what may have been added to the FOs in the manufacturing.
Second, make sure that they are "skin safe" and not candle fragrance. Eos and FOs that will give problems are some white florals and scents that contain spice; IE clove. Failing this tact, what were your temps of the lye solution and the temp of the fats/oils? Make sure that these are body temp and close to being the same temperature. You do not require a thermometer.
Stick your finger into the oils; you should not feel any difference in temp between the finger and the melted oils.
With the lye solution, feel the outside of the container that you use; there should be again, no difference in the temp.
I have even made the lye solution the night before and used the next day without rewarming. Caution about leaving lyeout, of course.
I add the lye to all ice cubes in a container, and within 10 minutes or so of stirring, I will have my lye solution close to the right temp. It can be a good idea of warming the scents to room temp, I do not need to do this, but it can depend on the storage and the prep.
You can add some of the oil from the recipe, or what I would do is; I melt the oils in my microwave (yep, it's large) and after the bucket is removed, I could put the measured scent in there just to sit.(Don't forget it though!) | 
