Sooby yes, those have some salts in them, But they are not salt based, as in miracle grow and most ammonium nitrate fertilizers. I have been switching over to a new line of ZERO salt fertilizers, fish and seaweed based, but until I see the result I wont recommend them.
As for seed mix- I use PRO-MIX® BX BIOFUNGICIDE™ + MYCORRHIZAE™ as my base, add 1/3 vermiculite, 1/5 perlite, and biochar. Top with play sand for gnat control.
I bottom water, I use ROOTMAKER 32 cell trays.
These are about 3-4 weeks old. These are some of the better ones, I have some 6-7 weekers that are slackers.
I control Damp off with Ban-Rot
I have about a 5-10% damp off rate with no sand and No ban rot. Have not had Damp-off on the trays I treated with ban-rot and sand.
I also temperature control the room at 66-68 degrees, and use two fans.
All my lights are HO T-5 fixtures, 2 lamp- 108 watts Using a Vegetative growth spectrum lamp.