aggressive behavior & sexing angelfish

[angelFis]

hello guys. i have 4 angelfish & they were living peacefully but since last week two of my angels are bullying the other two..i read online that they will be territorial when they wanna breed..is that so?? and help me sex them.. please and thnx in advance.
http://postimg.org/image/uorr4k5b3/
http://postimg.org/image/hlw4laf33/

[angelFis]

http://s27.postimg.org/69jj3i6eb/photo0106.jpg

http://s27.postimg.org/clyodc9gj/photo0108.jpg

[Ryan]

There is no 100% reliable method on sexing angelfish until you observe a spawn. The breeding tubes will be different on the male and female. Females will also keep a more rounded abdomen, which is more noticeable when they're ripe with eggs, but this doesn't show up on females until they've reached sexual maturity.

Angels will be territorial when they are ready to spawn. They usually start by selecting an area of the tank and guarding it from other fish. You'll also see one or both fish cleaning the site with their mouths. This usually happens for a few days prior to the actual spawn. It may be a male and female, or it could be two females. Same-sex pairs are not uncommon.

[angelFis]

thnx