I placed my Streptocarpus 'Falling Stars' on a glaringly sunny southern windowsill from December until the beginning of this month (March) and it absolutely loved it. It never once lost its deep green color or stopped producing countless flower buds. I noticed that the leaves produced with this much sunshine tended to be much more compact than the shade-produced leaves. However, the plant started to look a bit pouty with the increasingly strong sun rays of spring so it is now in a very bright eastern window and is now a gigantic mass of bloom.

Streps do well under lights. Almost all gesneriads do well under lights unless they get too tall. If the plants are sickly it could be something else--crown rot? bugs? bad soil mix? who knows? Try propagation. That usually is the best way to cope. Put down leaves and get some backups going. Have more than one of a given variety, so that you can try them in different locations, mixes, etc. Enclosing plants under plastic or in terrariums under lights is often a great way to revive a sick plant.

Joe,

Sun is probably not your problem. I have grown streps at my south and my east windows. The only problem I've had was burning of the leaves in spring at the east window.

I am wicking all of my streps and feeding them half strength Schultz fertilizer. The soil mix is 3:2:2, soilless mix:perlite:vermiculte. You might want to check for soil mealy bugs too.