Stop smoking MJ, first and foremost. When used regularly, it makes your brain lazy in all possible terms. Not only memory is affected by it but also willpower, self-discipline, ability to focus and other things. In fact, systematic MJ use is in direct conflict with what this forum is about, OSIT.
If you have problem giving it up, i recommend trying a plant called kanna (sceletium tortuosum). Best in extract form. It's great for killing the urge and also supports brain recovery. Effect-wise, it's a combination of a SSRI-type antidepressant and a subtle stimulant. It's safe and non-addictive. Works wonders for me (but it's not about cannabis in my case).
Also, nootropics can be helpful in memory recovery.
PS. And, of course, take to your heart all the advices about diet and supplementation.