dude, get a ph testor. They are like $20 on ebay if you can't find one at your local pet store (for aquariums) for cheaper. Ph up and Ph down is cheap as hell and you don't need very much of it to do the job.
As far as nutes go, by the size of the fan leave the plants are likely ready, and it could be a Nitrogen diff. from what I have seen in other threads. Or a combinination of overwatering, with bad ph'ed water, and possibly Nitrogen problem...