Pythium or not??

Hi guys! I really really need your help now and this time around I´m more confused then ever??? I am now in a single DWC 5G and the strain atm is feminized Blue Mystic atm (before that swiss cheese). First swiss grow went ok for 2-3 weeks before roots starting to turn color to a light beige/brown and got darker for every day + stunted growth, plant it self vener wilted or changed in appearance only stopped growing + I couldn´t see any slime on roots/in res just colors.. Is this pythium? This particular one has been in the bucket for about approximately 1.5-2 weeks now? Although on the 12:th (or was it 11:th??) of June I carefully plocked away the stones in netpot one by one to have a look and it had only managed to get through 1/3-1/2 way down the netpot so I did lower it a bit to get the root tail out the net pot by 1.5-2cm approx? Nothing have happen since then either, it just refuse to grow?? I will soon rip it away again and this will bee 3:rd failed one in a row and I´m going crazy here! The 2 before got more time (3 weeks?) on them before I removed. It´s one thing if I can see even a mm of growth but nothing! I have scrubbed all DWC gear properly in between and H2O2 everything, is rot really that resistant? I have one last thought and that is: Could it be the Hydroton even though I washed and bathed it in strong H2O2? Everything else is perfect, from very weak nute solution (140ppm water + 60ppm nutes) to scrubbed equipment, PH 5.8, water temp at 68-70F (chiller), new bulb, ballast, cleaned tent, air temp of 75-78 (AC) etc, 15l/m HighBlow air pump + large round disc.. This is driving me nuts and to see others explode up is not exactly encouraging, lol.

Kinda' sounds like pythium. Got any root pics?

Grow well,
B.B.