My water lilly is approaching its first full season (planted last
September). It has about six leaves on it.

Since it's in 'new' soil, a mix of kitty litter and loam, do I need to
fertilize it? If so, when?

I'm in zone 10b (So. Cal) and, water temp is fluctuating between 60 and 70
deg F. When should I start expecting to see growth?