In the mean time, quit runnuing water thru. If possible, wait till soil dries out a bit before adding anything else.

Fan leaves are a nitrogen storehouse, and will slowly 'give-up' the nitrogen as the plant needs it in flower. They yellow, and eventually die off. (a natural process)
They also yellow (with brownish-grey blotches) when they are being overwatered, and root rot is setting in. (a natural process preceding death) Only takes a couple of days of saturation before big problems develop.

Would recommend you do as stinky said a.s.a.p. tho.
Also, I'd hold-off on the H2O2 till someone can look at the plants.