Need second opinion

My friend has been having problems overwatering his plants he's 6 weeks into veg in 5 gals using soil etc.... I've tried pinning the problem down for a week done all the usual steps, now this morning he decided to tell me when he transpanted he put a layer or vermiculite at the bottom because he thought it would help with drainage. I know vermiculite retains a lot of moisture and I think this is his problem but before I uproot the fuckers to try and take it all out id like to be 100% sure it is this

Thanks

Just let them dry up and water less? I'm not a big fan of messing with the roots especially in 5 gal buckets to easy for root damage and unessary stress on the plant. Drill more holes in the pot sides and all , it will allow air to help remove the moisture from the soil and it works as a air pruner for the roots

How big are the plants? With 2 people you should be able to just lay it on its side it, pull it out of the bucket, - dirt, rootball and all,- clean out the vermiculite, add rocks, stone, dirt, etc, then put it back in. I've pulled 3'+ plants like this, even a 5' avacado tree I needed to root prune.

What soil did he use? Most needs to be mixed heavily with perlite, etc, otherwise it's too compact and holds to much moisture.

Plants are about 2.5 ft tall but really bushy I made a little jig and we pulled the pots of and it was fairly wet at the bottom I tried pulling out what vermiculite I could without damaging to many of the roots there was maybe an inch thick there's about 5mm now and I replaced it with some more soil and just mixed it in hopefully this will sort it

Plagron light mix