Soil brand suitable for Tiger substrate?

I have a Tiger Sal I found last November. He has done very well with Coco fiber as his substrate. Only thing is as most of you know the stuff sticks to him and I wonder if that might be irritating. I see nothing to indicate that it is bothering him but the truth is I don't like it either.

In March I put him in a new tank and tried a substrate of coco fiber mixed with topsoil that I purchased at Lowe's. In a nutshell I think I almost killed him. After a few days in this new tank I found him on the surface lying on his side and very lethargic. I've never seen him behave this way before or since. Luckily I still had the old tank with the old coco fiber substrate so I put him back in that. He slowly over a week or so recovered and started acting normal more or less except that he refused to come to the surface like he did prior to the tank change. Maybe he was a little traumatised?

Anyways these days he is doing well and has just started acting like he used to coming to the surface for food etc. But he is still in the old substrate which I wanted to change out back in March. I would still like to try some substrate that doesn't stick to him but I'm afraid to experiment with something that might hurt him.

So do any of you have any specific brands of Topsoil you've used successfully? The lady at Lowe's did indicate that the bags I bought were a new product this year for them. Or do you have any other suggestions for something safe and better than straight coco fiber? If not I will just stick with the coco fiber since sticking to him has to be better than killing him.

Most burrowing substrates will stick the the salamander, it doesn't irritate them, but I guess an alternative is moist paper towel that's changed everyday, but lots of hides would have to be provided and a pH safe moss might work as well.
Did the topsoil contain any fertilizers, pesticides, or peat? Any of those could cause issues to the salamander.

I use Zilla jungle mix. Even though if he burrows it sticks to him, it easily comes of with water, and holds humidity well

It said it was just topsoil but didn't list any ingredients. It had a lot of small sticks in it so I sifted it thru a course screen before mixing it with the coco fiber. I really have no idea what might have been in it. Just wondering if there is a brand or source that thru experience is trusted. I don't want to take another shot in the dark but I need to do something soon. I may just use coco fiber again.

I use coco fibre, the tiger just go for a swim if they want to get clean.

But they seriously prefer to be covered in substrate....

I find a mixture of clay rich top soil and coconut fiber keeps the substrate from compacting, and holds their burrows up really well.