Possible root problem

This is my first grow, single female plant, 2.5 months veg, now 6 weeks into flower. I have ran into a few more problems. The leaves are yellowing and falling off at the bottom and center of the plant. I don't believe that lighting is an issue, although I am trying to flower w/ only 10 - 26w CFL's and a 40w grow tube light, the plant does seem to be developing fine. I say "seem" because this is my first grow and I am not sure what the plant should actually look like 6 weeks into 12/12. The petioles have also taken on that purple-reddish color to them recently and even though the plant is in a 4.5 gallon pot the roots have started to show through the bottom of the pot from the drain holes and they are even starting to poke out of the top of the soil. I have to water with 1 to 1.5 gal of water every 3rd day- could probably do that every other day as the pot feels without water the day after- weight difference. For some reason I was thinking there may be a root issue and then i noticed the roots showing from above and below and was wondering about repotting 6 weeks into flower. (temp. between 75 and 85)

So, my questions are, can you repot that far into flowering without hurting the plant- and if I repot can or should I remove some of the root mass? I reallly thought 4.5 gal pot was big enough for a 36" plant.

also, are the leaves falling off ( 10-12 over night ) as a result of flowering or is there an other underlieing factor to consider?

Thanks for the help-

sounds like the problem i had recently out of a 4 gallon pot. i transplanted in wk 4 without any shock. most on this site were against me doing so but i was proven right. you have to do what you feel is right for your plant..

That pot sounds easily big enough. I would keep it in there. Fan leaves do yellow and fall off during flowering as the plants are sucking up the sugars stored in them. 1 day you can look at them and there may be no yellow leaves, but the next there could be 10.

What do the yellow leaves look like. If the veins are still green, but in between are yellowing, it would prob be a magnesium deficiency. Add Epsom salts.
If its universal yellow = nitrogen deficiency or as i explained at start but at this stage thats expected. Plants dont need a lot of nitrogen at this stage as it will promote leaf growth and so u'll get more leaves in with ur buds

it has out grown its pot. scroll back up and read what he said. the same yellow leafs occur when this happens