Ver bad burn problem....any advise?

ive got a plant that has been growing in organic soil and been outdoors..i am giving a small amount of miracle grow all purpose(i knoiw not the best to use) every week and watering 3 times a week...ive read not to water that much so i brought it back to once a week, the nutrients then the water the folowing week ..my plant doesnt seem to be getting very big and now some of the lower leaves have shrivled up,dry to the touch and are turning bright yellow like they are burnt and it happening to the whole leaf not just the tips....and a couple of the leaves at the very top... the tips(some going an inch back)are burnt as well but bot the whole leaf its just the tips...i tried a flush by overwatering the shit out of it thinking maybe a salt buildup or something and i think its almost made it worse....any advise would be of a great help....thatnks alot guys

Too much miracle death. They need to be flushed but being out side i do not know. Maybe an outside grower can help. It would take a huge amount of water to flush. I had this happen one time outside and nothing I could do.