hi, it is normal for them to rumble they should calm down soon though so long as there is no fighting which ends in bloodshed it is fine. They are most hormonal in teenage faze which generally ends around 14-16 months old.
With regards to the waxey lump this is their greese gland if not cleaned regularly the build-up can lead to skin problems. depending on how greesey they get they will need cleaning at different intervals but ideally should be bathed every 6 weeks or so. If they need their glands cleaning more frequently you can do a "bum bath" where you just clean the effected area. This also does calm down once they have finished their hormonal faze.
Now I'm not sure what products you have there but in England a great thing we have is swarfega which is used mainly by people who do dirty jobs and want to clean their hands well, it is good for getting car oil etc off your hands.. other people use washing up liquid, though I have never tried this method.
You place a small amount onto the gland and massage in, leave a few minutes and wash off, them shampoo the guinea with safe guinea pig shampoo all over. There are more details on bathing in the daily care threads.