Delisted does not necessarily mean having no value. Are the companies still in business? You have to “realize” your loss, meaning either you sell the stocks to someone else, even for some very low value (your broker might help you with this) or you have to have some declaration that they are actually worthless, not merely worth very little.
Also, any losses from 2012 or 2015 are too long ago to actually result in a tax benefit, even if you claim them. You would need the realized date of the loss to be in 2016 or later, then you could claim the loss on an amended return and see if they gets you an additional refund.
