Hmmmm
well by the looks of things how long do you think i should veg?
theres no way of telling sex until flowerng right?
On another note it looks like bottom left might kick the proverbial bucket.
That's tough Katie I don't want to discourage you but five fully vegged plants in that system are going to be crowded to say the least. You are asking the right questions though, topping is a good techniques for increasing yields. I would also trim the bottoms as they veg it will for the plants to concentrate on the tops/colas. This will also keep your plants from getting too bushy and cramping each other. Here's the thing with preflowers, some plants show at 3 weeks some t a month some don't show til flower, it's a crap shhot and depends on the strain, pheno, and the enviornment too. There are too many variables to try and guess when you are going to show preflowers. If you veg a month and trim you should be fine if we say that 50% are going to be male. Also vegging for 2 weeks will provide less yield but it is speedier and more geared towards SOG grows. Also when you top it takes a little while for the plant to recover so do a month and see where you're at.
Also Katie on a side note if you go into my gallery the first pic is 3 plants at about 4.5 weeks since they were germed. Only one turned out to be female and I am glad.... see that mess....trimming is key. I wish I could show you what the one survivor looks like now but the ex took my camera to teach me a lesson...lol. Anyway she is huge and I have had huge problems with it. Some questions you want to ask are how high can my plants get especially with a HID light, they double and sometimes triple in height when flowered. Good luck, if you have problems everybody is here to help, I am also responsive to PMs....you're doing great and asking all the right questions, good work....puff puff.
Also if you look through my gallery I have some female preflower pics.