Low light will definately kill anemones. From my experience, Bubbletips are one of the hardiest clownfish-hosting anemones, but two 15w bulbs on a 25 gallon is definately not enough light. I would reccomend an absolute minimum of 3.5 wpg
for the bubbletip.
Anemones get most of their nutrition from the zooxanthellae algae that lives within their cells. This algae needs intense lighting to carryout photosynthesis, producing carbohydrates and organic acids. This provides for much of the anemone's nutrition. Anemones are believed to also "feed" on the nitrogenous wastes produced by clownfish, but many experts believe the waste is consumed in order to provide nutrition for the zooanthellae algae. Anemones also have the ability to collect planktonic organisms in the water column as well as an unexpecting fish or invertebrate that is caught up within its tentacles.
Most clownfish will not feed their anemone. I'm sure a well fed clown may bring back some food to the anemone. But I've actually witnessed clownfish taking food away from the anemone. I would not worry too much about the clownfish physically bringing food to the anemone. However, I believe it is the owners duty to offer the anemone food (shrimp, squid strips, scallops, etc).
You might also want to consider water quality and tank conditions. Anemones require intense lighting, proper trace elements, low nutrients (phosphate and nitrate), as well as good water movement. HTH