I ran DWC for a while in 5 gallon buckets, then I did a little recirculating DWC as well, and run mothers in DWC now. Switched to Ebb n Flow not too long ago, actually my first Ebb/Flow harvest is scheduled for tomorrow, and I've already cut 5 plants and have them hanging. I did SOG and started with 43 seedlings, 12/12 from seed.
PPM is usually strain dependant, but you say you've been using full strength nutes according to the feeding schedule? Maybe try to start tapering off a little, down to like 3/4 strength. How long do you think you're gonna flower overall? It's been 7 weeks since you put them under 12/12 lighting or 7 weeks since they showed clusters of pistils?