Hi Micca, I do have some Epsom salts I actually put a bit in the mix. My potting mix is:
Baileys premium 30L
Perlite 4L
Cow manure 2L
Handful of rooster booster
Also a tablespoon of Epsom salts and a table spoon of dolomite lime
Once every few weeks I water with Thrive for veggies.
My OW plants are a decent size and seem happy, they look great, grow fast and have a nice healthy shade of green. They are also producing buds like crazy. All my plants are in 25L pots with extra holes drilled for drainage and I'll be putting some white tarp like plastic around the sides to keeps the roots cool when it gets hot.
I also sprinkled a small amount of potash on the top soil a month or so ago.
I'm thinking they should have everything they need, without overdoing it.. hence my annoyance when the first few flowers have dropped lol