Transplant soon, give plenty of sunlight and don't defoliate.
Your plant needs every healthy green leaf it has to make the energy it needs to grow her biggest and best flowers.
20 litre pots would be a sensible minimum size and fill the pots right up to the top, this gives maximum room for root development.
Feeding half strength nutrients more often is better than giving full strength less often.
By this I mean, half strength every 7 days is better than full strength every 10 days when growing in soil outdoors.
A gentle constant "trickle" of nutrients is better than nutrient spikes by feeding full strength.
Top dressing your pots with worm castings will benefit your plants.
Adding some mycorrhizae fungus to your soil mix will help extremely with plant health. "Mykos" made by Xtreme Gardening is awesome and worth every cent. Similar products made by other companies will no doubt also work, but I have only tried "Mykos" and can only recommend this brand from my experience with it.
Finding a product with amino/fulvic/humic acids will also benefit your plants greatly, and all three will do wonders. Don't use molasses it is BS and will not do anything for your plants. A mineral mix of trace elements is also well worth giving, as is bone/blood meal and finding a quality seaweed tonic/extract will be a general health booster to use all throughout the plants life and can help your plants cope with extreme high or low temps. Most importantly, don't forget to love them! If you are really keen, some classical music once in a while is soothing, especially piano concertos, but that might just be me!
Mandala Seeds also have an awesome "grow guide" on their home page that is full of superb information.
Hope this helps, Organoman.