OD, I'm not sure what could cause an issues- but I would just add that you should not try to upp thyroid meds dose or something- as its possible that your cortisol is bit down.
Now- cortisol is transporting thyroid hormones in cells and if cortisol is insufficient obviously they will pile up- now when cortisol goes up- it will start using thyroid hormones (and if it is a lot there it could potentialy cause thyroid storm)
If your thyroid hormones are too high compared to cortisol you will have irregular heart beat and feel weak, worn out.
Other option is that your thyroid hormones are bit depleted from tren if that's the case it will take you couple of weeks to get to the point where you'll be able to continue your cut.
In any case probably best option is to wait.