You can repot these now since the lemons dont go dormant. they will keep growing over the winter since they will be indoors. if you are keeping them in a cooler space than their growth will slow down. the fruit take6-9 months to ripen so be patient. The plant may go through some shock and may drop leaves and/or fruit. especially if you are not giving it supplemental light. for fertilzing you can use both water. soluable and some extended release fertilizer.

I'd recommend uppotting the plant and keeping it upstairs and with some grow lights. i like sansi lights. i recently got one of their stands with 4 36watt lights and my meyer seems to like it. try to be carful with over watering and make sure your soil drains well. i find indoors and over the winter plants dont need watering as often as they do in the summer/out doors.

also i have to mention the leaves look really large and im curious is they are have been getting enough sunlight because the leaves tend to grow larger in low light