I kept this begonia plants as indoor and leaves turning yellow…is that because of no sunlight??
There r around 1800 species of begonias and most of them prefer indirect filtered light, though there r exceptions. So keeping them near a bright window sill is good option. Also they need good fresh air flow around them which is deprived if we keep it in deep corners of our house. Keeping plants away from their daily sunlight requirements make them starve and weak and with loss of immunity leading to them being prone pest attack. The yellow spots could be fungal attack due to above reasons or due to root rot due to overwatering. Please move it a bright light spot, water only when top soil upto 1-2 inches is fully dried out, spray natural pesticides (already listed in our HS tips section) on leaves. If too much infected, leaves can be cut off. Fresh leaves will come with good health and vigour devoid of yellow spots.