yeah, i always preach preventative gardening, really checking out and getting deep into the environment and the rhythms of that area. In your area its humid and moist from your proximity to the river, and on top of that you get a high amount of rain fall that tells me that you have a high chance of dealing with fungal activity, molds, mildews, and the like. Cannabis is highly susceptible to fungal attack, either PM or Bud mold, but also stem rot can occur. If i were to chose a spot and set up for these conditions i would choose the highest and driest area on your property and put raised beds or ideally fabric pots with a lot of spacing for verity of reasons. I would avoid too much cover cropping and mulch, not cut it out but just less, have tons of room in between each plant, and make sure to keep the area in between and around clear of weeds. Sun light, heat and wind are the best killers of mildew and molds so i would plan accordingly.
Sorry to break it to ya but you have created not ideal conditions for your plants, you have low drainage in your media, coupled with it being in a clay pit you probably have excess water causing a slew of issues. On top of that your plants are low and somewhat sunk into the ground, not too much air flow or light getting to the soil to dry it out. Having live composting in your beds and a lot of cover cropping/mulch from it it a killer idea but imo in your spot its a bad move, adding to the chances of having mold, mildew and rot.
Put your soil into pots or beds above ground some where hot and sunny, make EWC in tubs or beds and use after composted, and keep to your cover cropping and companion planting. Mix out your cow with peat or coco, get some fresh compost and some pumice/lavarock/pearlite/ ricehulls and make em' 200 gal pots/beds if ya can!! You'll grow pounders for days, and could easily achieve multipule per , promise!!