Doctor Please

Ok, heres the deal, these two plants were a dark green plant until i changed the water 5 days ago, now on one, i see a leaf has a dark spot on it, and the bottom bigger leaves are sagging slowly, and turning a light greenish yellow, ive done some reading on here, and thought it was maybe because of MG def. and added epsom to my system, then i turned around and read it could be a ph issue, when i changed the water, the water in it had kept fluxuating back and forth in ph, i was using whitevinegar to buffer it down, and it wouldnt stay down long, ket showing at 7 ph, but the plants were still very dark green, now the ph is at a 6 in the system, and im thinking maybe the heavy drop in ph is what has caused the spot on my leaf and the other leaves to turn and sag a lil bit, so.... what to do in this situation i have no clue.... should i empty out my res and redo the water back like i had it beforehand, or leave it with the new ph and epsom salt in it. i put 1 table spoon of epsom per gallon, theres exactly slighly over a gallon of water in each of my buckets, the roots on the plants are awesome looking and fine, and new growth keeps appearing and coming off the top, any suggestions will be helpful, as so many of these symptoms sound similar and on some of the posts in here i cant even see or access the images to check them out

the same one with the spot on the leaf, here is a top view of it as well

also one thing i should mention, i hadnt used any nutes on it at all up until 5 days ago, i added half a table spoon of grow big and half a table spoon of big bloom to the water, thats far below the dose for that size plant according to the guid i have

another thing, i have 4 plants there is only these two, that have the issue, and all have the same set up, only one has a spotted leaf, lol, so id ont know what in the world it is or if i shouldnt sweat it or if i should flush out the nutes and just use ph'd water until a few more weeks have gone by, the water here is well water so its soft and is why i believed there was a MG def going on