Help!! Plants looking sad

Im 5 weeks from seed. Just transplanted to 5 gallon from 2 gallons. Growing in 50/50 pro mix and perlite. I feed them 400 ppm last week they looked really good the next day. The following day they looked all droopy and over fed. I flushed with 6.3 ph water. The run off was 500 ppm. 6.1 ph. Waited a few days and gave them more ph'd water. Still looking bad. I transplanted them hoping that would help. I gave hem some water this morning and they are showing no signs of recovering. This is my first soilless grow. I've had nothing but problems. Any ideas? Thanks

Maybe overwatered? Since the roots haven't reached into the 5 gal it will stay wetter longer. Just a guess. Do you have pics?

I don't think it's over watered. The mix is very airy and water runs threw. Should I be letting the promix dry out? And I've heard that salts build up in peat and it should be flushed regularly. I'm also curious if I should be letting my pots sit in run off or should the run off be drained and wasted.

Run of drained and wasted for sure. To me they look overwatered but maybe the roots got a little damaged and stressed her during transplant?

You can generally expect some stress for a week or so after transplant. They do look a bit over watered. You for sure don't want your plant to sit in stagnant run off. If you have no way to get rid of run off try setting your plants up off the bottom of a rubber made tote, drill a hole in the bottom and put a fitting in it. Run some hose with an inline low volume pump out your window or where ever. If the pump isn't possible you can use gravity. The biggest point is to not let them sit in the run off. It can water log roots and over time change soil ph. Also you could check into a small ebb and flow set up. Just a thought.