It's really hard to say...when they are older (3 yrs plus) sometimes there are tell tale signs, but even those can be wrong. I think my 1 y/o is a male because of the way he started acting...most of my males are a bit nippier than my females. But at the same time, you never realy know. Even with DNA sexing, there have been mistakes, not alot but that's not always accurate. I had m ost of mine S/S and even when they were young it has proved (for me) to be accurate.
Good Luck
I really like the Lafeber's pellet also. But a few of my greys seem to toss it. I use a mixture of Zupreem, Lafeber and put in a smalll amount of Volkman Featherglow seed. They all get a soft food mix with fruits, veggies, beans, rice, etc. everyday also.