Pure lemon oil can have a drying effect and isn't a suitable conditioner.And in many other parts of the country, the neck will forward bow at this time of year.And for some basses may go the opposite way in each region. It depends on the local climate and the individual instrument.
I have a bass with a finished maple neck and thick, unfinished ebony fretboard. It used to be very sensitive to humidity, but that sensitivity has decreased since I've been applying pure lemon oil to the fretboard. It usually gains relief and needs a little adjustment in the fall/winter when it's heating season and the humidity in my house is lower.
I agree with @Zooberwerx that a little truss rod tweak should solve your problem. See ALL BASIC SETUP QUESTIONS ANSWERED HERE, download the Fender setup guide. IIRC, .012' relief is a good starting point. Fine tune the action and relief from there so it plays evenly all up and down the neck, your preferences will probably be different from Fender's average setup.
I would guess that your conditioner is mineral oil with lemon scent added, also not a great choice because it comes back out on your hand over time.
Linseed oil from the Art Supply Store is a better solution because it's a drying oil which will dry over time and stay in the grain pores.
My dad did oil changes and tire rotations on the family cars. He even had a set of point files for the distributor rotor (I still have them. Handy little guys.)! I think that was mostly for the Nash, but maybe for the Chevy Impala, too. Point being: It made sense to know the basic mechanics and maintenance of the stuff you had. Cars (and lots of household appliances and whatnot) have evolved tremendously since my dad was filing rotor points in the 50's. Entirely new skill sets are often needed. Basses, on the other hand, have not, at least on the mechanics side. Materials and processes are fundamentally the same and maintenance hasn't really changed, so it makes sense, IMO, to learn the basics of "care and feeding" of your new (or old) bass.
