There's not really any doubt that you will be losing muscle mass at a painfully fast rate. This happens to a lot of people when on a calorie defecit even without the complete lack of protein and fats. I seriously suggest ditching the juice diet as quite frankly they are completely rubbish. Juice is absolutely the last thing I would suggest someone looking to lose weight should be consuming. Sure it might work, but there are much easier and more effective (long term and short term) ways to skin this cat.
At this point I would be trying to limit sugar and get your insulin sensitivity back in check. This means fats, protein, lots of veg, careful use of carbs and monitoring of calories. It's a very easy thing to do and will not only be more effective now while making you feel better, but will put you in a much better position to make continued progress.
Again, thanks for the input, honestly, but you know - telling me to ditch what I'm doing isn't needed. I've been through many years of nutritional research and struggles, which if you see my videos I know what I'm doing and I plan to to stick to it. This whole year is planned to get me into a better place, which took 4 months of planning itself. I'm aware of the things I'm going through, I will lose some muscle, but I have planned to regain that with the continued diet and training. The juicing isn't a diet, it's a fasting phase that starts my plan to change my lifestyle.
One thing I've learned is that everyone has different approaches and very rarely does someone not feel the need to tell me why theirs is better

Plan for this year in brief...
Juice Fast > Whole Foods, Plant-based diet > reintroduce lean meats and avoid gluten (possibly lactose too).
As well as exercising to my ability level
DDP Yoga > Krav Maga > Running > More intense training (considering CrossFit)
I've put as much support and motivation in place as I can.
Blogs > Video diary > Twitter and FB support > Focusing on Spartan Race as a target with best mates and raising money for MS.
I honestly don't see a problem. I know this forum is very weightlifting-centric, which is cool. But I'm not trying to do that yet. I can barely do a press-up!