my lemon trees are dropping leaves and í just notice the tips getting brown...i think it wasn't enough light so i just bought a grow light 2 days ego..i also added some citrus food on the soil....should i wait to see if tha was it....they were growing fine while they were outside, but because of the cold í brought them in about 2 months ago, and this started about 3 weeks ago...í dont want them to die!

II dont want them to die...what should í do?