Seedling Problem. Maybe mold?

This is my 2nd grow and my first time using dwc with drip Indoors. The plants are 3 weeks old and the 2 of them the stems are started to turn brown. Could this be stem rot? i Couldnt get good enough pictures to see but ill try to get some . Also my res has a funny smell and the ph raises about 1.0 every day is that normal for dwc? Im using foxfarm nuts Grow big(For Hydroponics).

You're using nutes on seedlings? Let them grow, and see if it might just be the strand...

(This is adannyboy4u I couldnt access my account)
Yes im feeding seedlings.. Im only giving them 25% of recommended dose. I have always started feeding after 2 weeks or when they have roots. But about my problem it seems my tempature was in the lower 80's im keeping it around 72 and the smells has left and i think it might recover. Would changing the temp of the grow room and res kill off the mold or whatever it was?