are we talking 1 or 2 tsb per gallon? or are we talking about a heap mixed into a gallon.
im betting its the former rather than the latter. i don't know much about MG products, personally id start with 1/4 of the reccomended strength every other watering or so.... see what happens.
the MG stuff i remember;it was like blue crystalline stuff, usually had way to much ammonium and 0 calcium and 0 micro nutrient chelates, you might find you need other fertilizers as well.
im not up with the MG stuff, i understand they make fertilizer for those hose attachments?...that stuff is likely way to much for a single water in application. make sure you are not mixing a fertilizer for that type of application i guess.