Help PLEASE, babies need HELP! SPOTS, YELLOWINNG, SHRIVELING the works! =[

Vey new at this have a few nice looking plants but my favorite plant just did a 360 on me. it stated gettin dark spots edges turning brown then leaves started turing yellow. after all this bottom leaves stated shrivel up, since then ive cut the dead leaves off... Im not sure if i gave em too much nute or not i been pretty much freestyling this poject to get the flow of things, HELP! look at my pics and lemme now what you think and any solutions....

can you post a pic of the full plant plz?

sure give me 3 mins

Appears to be a Ph problem.

PH huh... Damn, ummm ok so there we go like i said i hvnt been checking PH or anything i just been doing this free hand i have some pretty nice plants but this one just fucked up on me =[. So where do i go from here, 1 purchase a PH testing device, 2 do i transplant into new soil or buy poland spring water and start with that? I know the water in my area is super bad...