Help PH Hydro crashing low everyday

Thread starter #1
Well I need some desperate help. My plants look fine but starting last week the water kept dropping into the PH 4.5 range everyday 3 days in a row. Well I said fuk it and changed the water and soaked my plants all the way up to the top of hydroton in PH 6.0 water (trying to flush it out). Well after 2 days of good water, today I goto check it and the PH is back down to 4.9. I am using benificials and aquashield in the water. I got hard water like PPM 400 but the other bubble bucket is fine its usually always at PH5.8 and sometimes up to 6 but its the same water and never drops down to the 4s. I am using AN 3part GH calimagic, GH armorSi, Botanicare aquashield and Plant Success Orca. My roots are pretty white but up deep in the root ball above the surface of the water there looks to be a blackish nugget of roots inside all the white root. Its been there for 3 weeks but CAN it be root rot (would that cause my PH to drop)? My water smells OK and is clear except some pieces of root that break off when I add bottles of frozen water to keep temps down. WHATS UP ANYONE?
 
Can you get us a picture of the black roots in the water?

Any update to your issue?
 
Thread starter #3
My roots ya they are white and about 2 to 3 feet long and crisp its just a little tiny nugget up right where the knot of roots form outside the net pot. I can even stick my fingers up next to it and gentle feel around the area all roots seem nice and crisp. No slimy feeling stuff no drooping roots. Lot of side branching all along the length of the roots, but some pieces are breaking off in the water and floating around in there probably from the ice bottles I put in the water? I pulled another gallon of water out and replaced it with plain tap water, and the PH is holding at 5.8 for 4 hours now. I'm going to check again. I cant hold the pot and snap a picture at the same time its to heavy.