if together they are about 1/2 the area, then it's about the right time (or 1/2 the area in a week or so, more accurately)
when you have filled about 2/3rds Length and 2/3rds width of space you can cover in flower, it's generally a good time to flip. Some plants triple in size and even this may overgrow a bit.
if you just tied them down, definitey wait and see... some stall slightly after extreme LST. Some do not. If you see some funky leaves don't worry, it'll grow out of it.
i'd defintely wait for some axillary growth. Continue to train the plant so they all even out in regard to vertical growth.. temporarily tie down any dominant cola so it does not hog resources... release when other branches have caught up... and so on. Play 'apical dominance' like a violin until the plant is shaped to your liking. if you need alot more growth, keep them horizontal for a while and allow side branching to grow vertically. Timing really depends on the space you are trying to fill... and work backward from a specfic goal... llike 1 vertical cola per 5in x 5in or wahtever... then make it happen in an organized way to save time.