Yes that's a bacterial infection. Its going to be a battle. Im assuming your in a DWC and not a RDWC.
Directly spray the roots with a 3% mixture once every 2-3 days and do a bucket change.
Every day add 2ml/L of h202
@3% to the bucket.
Keep your usual feeding since your using synthetic nutrients which can be used in a sterile environment
If you can add more air stones the more air the better.
Keep the air pumps outside your tent( or even in a fridge ) to keep water temps down.
If you can keep the water temp at 65F and never let it get above 70F( or below 63F).
Use frozen water bottles and have your bucket sit in a larger tote with water in it and keep that water at the correct temp which will keep your bucket water correct.
Get some white paper and place on the bucket top to block light from hitting the black bucket and heating it up.
If you have access to hydro guard that can help, But its organic so it will be killed by H202.
Good luck and Happy Growing