First you need to clean ALL OF THE SYSTEM
1 remove you res. from the system and bleach the hell out of it.
2 run fresh water out of the buckets and clay balls
3 use a MILD solution of bleach and wash it through the system buckets and res. tank, lines etc
4 drop you ph to 5.6 for a few days, drain flush and clean again.
5 use some hydrogen proxide with your solution 1 table spoon per gallon. 3 bucket fills and drain cycles
6 start over with a fresh solutioins and a ph of 5.6
Watch you plants each day and find out what ph and ppm they like. you want a 1/16 to 1/8 leaf tip burn with a nice deep green leaf systems

And keep you solutioin temp in the low 70's f. to help stop any more grime/goo/etc.
A CLEAN SYSTEM IS A HAPPY SYSTEM
:thumbsup::thumbsup::thumbsup: