I'd get a good magnesium supplement; chelated magnesium, magnesium glycinate or magnesium orotate. You could also try a B-complex with methylcobalamin B-12 (avoid cyanocobalamin, it doesn't cross the BBB). That'll help to restore health. If you don't feel like taking all that and waiting for it to start helping you, you could get some of those Vitamin C packets and consume those once in a while to keep your tolerance down. All these things keep your tolerance down.
Zinc picolinate is also good to take along with magnesium