The meaning of words can become a topic of debate. It depends on your prior learning and association with. 

I like to think of self-care being things to nourish the physical body. E.g. exercise, sleep/rest, nourishing foods, fresh air, sunlight, deep breathing, having a bath etc.

Whereas soul care is doing things to nourish the mind, will and emotions. Of course, self-care can positively impact the soul, which is wonderful. E.g. you exercise and feel clearer and less foggy in your decision making and memory. 

But what are you doing to support your mind, will and emotions? Are you cleaning it regularly? If so, with what?

For me and my years of experience working in disability and having a serious illness myself, it’s so easy to address the visually obvious- the physical. Of course like in Maslow’s hierarchy of needs we need to address our physiological state (e.g. hunger, pain, thirst) in order to stay alive. But we often stop there, particularly when we feel pressed at every side, exhausted, burnt out from attending appointments and managing the diary with different therapists. This is the same for either the patient or the carer. 

We wonder why we still feel hollow, unseen and dissatisfied on the inside, even when our outside needs are finally met and managed (for a moment anyway). 

Soul care is addressing the truth about our belief systems, values and attitude towards our life (which are driven by our emotions). It’s extremely tough and not a lot of people want to go there because it’s exposing, vulnerable and ALWAYS a process. Whereas self-care you instantly feel good (thanks dopamine hit) after doing it. Soul care takes time, trust, accountability with another person (hence 'Soul Care for Carers' service). But the inner freedom that awaits you is precious, undeniable and lasting. 

I highly recommended reading the book Soul Care by Debra Fileta.