I'd agree with not enough light.
Even though you haven't changed anything in the way you grow inside, is it possible that any trees outside your home are now shading the window(s) that they are grown in more than they used too? That would be my guess.
Only other thing I can think of is the fertilizer. Are you using it according to the package directions or are you using it at 1/2 or better yet 1/4 strength. Weakly/weekly is best. Do you also give your plant a watering with just plain water to flush out built-up salts?
Other than that, I got nothing................
Judi