Howdy all!
I've got several fish that have started scratching themselves after I
started dosing the K2SO4 and KNO3. Doesn't seem that this is a good thing.
Any thoughts?

Tank parameters:
29 gal (just over one year old)
1 - 55w CF & 1 - 20w standard flourescent
CO2 (compressed)
pH: 6.8
KH: 2 (I've started bringing this up last night using baking soda - 1/4 tsp)
GH: I have no way to test this right now
Nitrates: 0 near as I can tell from my test kit
Nitrites and Ammonia: Both 0

I've started dosing both KNO3 and K2SO4 really low 3 days ago. By low, I
mean about .25 ml per day. Today, I just dosed the K2SO4 at about .6 ml. The
doses are well diluted and added slowly, so no chemical cloud. Almost
immediately after todays dosing, the fish started bouncing off plants and
wood again.
Also, some of the fish's tails are starting to look tattered. These same
fish are also running up and down the side of the tank. This seems to me to
be indicative of chemical poisoning, but as I noted, both Nitrites and
Ammonia are at 0.

Any clues? Has anyone experienced this before?
Darryl