I don't think there is a possibility for someone watching (be it live or on TV) to seriously differ between health problems and just bad play. His game is very risky, in general, so the line between triumph and desaster is always a very thin one.
What I just don't understand - given his health problems - that he schedules rather poorly. He has to pick his tournaments with more care and not entering as much as possible.
I think the same, actually don`t see any difference, but then - I`m not a fan and don`t watch all his matches. Maybe someone follows, always better ask.