What do you have them growing in now? If a standard potting medium, then you're using a soilless medium, too. The quality between potting mixes is highly variable.

My preferred mix is one that is mostly bark fines, plus peat and perlite. It drains rapidly, and is extremely porous thus promoting a robust root system. That means, of course, equally fast growing top growth!

Nothing should sit in water all of the time, by the way.

It's a mix I made, some potting soil for veg and compost. It seems ok but kind of cakey and fungus gnatty. Most of my plants do well and these just seem stagnant so that's why I want to try anew mix.

I have all the stuff for gritty mix, maybe do gritty but add some peat as you suggest? Culantro is supposed to stay very moist so maybe the peat will accomplish that.