We often have issues like this in life. Tactful diplomacy is required. Tomatoes need 'consistent' water. this means that if they are continuously wet, rather than damp, they will not do well. l If they are 'wet then dry' they will suffer from Blossom End Rot due to irregular nutrient uptake and if they are too dry they will be slow to develop and often flower while quite small so that the plant can finish its life cycle before it dies. Brown and shrivelled leaves along with blotchy fruit suggests they plants are affected by soil born viruses. Soggy, wet soil will exacerbate this. Moist good draining soil is ideal for optimum growth and yield. Crop rotation and planting virus resistant varieties is also a MUST to control or reduce the effect of soil borne diseases. Slaters are normally only 'decomposers' and would generally only attack plants that are very stressed. Mushroom compost is already 'spent' and while can build up the soil it also increases the salinity. Trust this helps.

- Ken