Yours symptoms do sound suspicious for a TIA, and this should be evaluated and followed. Your risk factors for atherosclerosis should be looked in to like diabetes, hypertension, cholesterol and avoid smoking, exercise and eat well.
The cause is not likely to be due to herbal medications and more likely to be due to intrinsic atherosclerotic disease in you r body.
DHEA and acetyl cysteine are thought but not proven to be protective against stroke/TIA. An extract from Matiake mushrooms is postulated to be protective against cancer, but no reports I found of TIA. Rhodiola is not associated with stroke/TIA, but is thought to improve exercise endurance, whether this could put more stress on a person already prone to stroke is not clear.
Blackcurrent oil is not associted with stroke and has been tried as a nutrition supplement in patients recovering from stroke ( as a source of omega-3 oils). Turmeric extraxt is thought to be an antioxidant (and therefore not assocaited with stroke) and astragalus is though tto be a neuroprotectant
all the above postulated effect are scientifically unproven and their postulated effects must be taken cautiously
Good luck