Ppm

Is 350ppm to high for seedlings day 8

Yes

Ya thats high. Seedlings don't need much other than moist soil and good humidity for the first couple of weeks. Are you adding nutrients already? Or that just your tap water?

Dwc
4 gallons in 5g bucket
Water was 151
Den added nutes it came up to 352
Didn't have ppm meter til today n tested

Added tsp of flora m g b

Im not a DWC guy but i think most fert guides will say seedlings should only get around 200ppms, or a 1/4 of the recommended strength, gradually increasing until they are well established.

Just use some cloning and seedling solution.