As far as what you’re looking at doing, that wouldn’t be harmful and can be very beneficial… but it may not get you completely back to where you were depending on what kind of damage those drugs have done. What I mean is that if the drugs damaged your brain tissues, taking these supplements may not be enough to overcome the damage… but if it’s just making your brain foggy, they can help with many aspects of that.
As long as you aren’t taking any prescriptions or have any medical conditions that would cause a problem with them, those supplements (Fish Oil, vitamins/minerals, DMAE, etc) are very good options for brain health and overall general health. The reason I make that disclaimer is because Fish Oil and Ginkgo both have some blood thinning properties so you typically shouldn’t take them with certain drugs and some medical conditions can cause a lot of issues if you take a blood thinner.
With all that being said, I used to have a horrible memory. It’s still not perfect and I’d like a few aspects to be better, but it’s never been as good as it has been since I started taking a few brain health supplements (Fish Oil and Ginkgo among others). I would also point out that I would only add one or two at a time just in case you’re allergic to any of them or have any negative reaction from them… that way, if you have a good week or so between adding each new one, you’ll know which one is giving you the reaction. Good luck and I hope I helped!