Yes I had these clones in a NFT system in the beginning but my water cooler broke and I had no money for a repair / getting a new one because of health issues. The roots started to rot so I put them in soil because a friend told me it was a cheap solution to get this grow through and also get rid of the rot. It worked.
Well if it is potassium deffiency it is most likely potassium excess because I run a EC of 1.2. (0.3 50/50RO-TW base)
Well then you're going to have some absorption issues while the plant recovers from the root rot, if it does. As long as you keep the soil from getting waterlogged you have a chance.
If they've been in the soil for less than 3 weeks you shouldn't be feeding at all, the soil will have all the required nutrients.
If that soil has mycorrhizal spores they'll colonize the roots, which can help plants fight off root rot, and makes a wider range of nutrients available to the plant. If not you might want to get some for future soil grows if you intend to do them.
Tap water should be fine. I've done side by side tap water vs rain water grows with a couple different kinds of plants, and they all grew the same, and the rootballs were pretty much identical. I was interested to see if that was the case since I use a soil with mycorrhizae and had heard horror stories about tap water killing them off. Didn't happen.
The chlorine and chloride levels are good to keep bacteria/microbes from proliferating, not really enough to kill them off, at least not in properly treated water.
