what you might have is a ph fluctuation associated with the rockwool,at two weeks old those plants should be able to handle a full strength application of nutes providing that the ph is adjusted to 5.5-5.8 after you added the nutrients.using urine is a very bad idea,especially in hydro,all that does is contaminate the reservoir and the nutes in it,good quality hydro ferts are used by the plant instantly and they should contain all the secondary and trace elements as well as the major needed by the plant,with rockwool you must check the ph every day and adjust when necsesary,and it has to be stabilzed before you grow in it with a ph down solution of 4.5 for 24HRs,also keep the reservoir temp at around 65-68fh....bonbon
http://www.highlife.com.au/man/growing.htm