clones smell bad!!

so im having an issue with my clones. ive been a cloner for about 4 years and have never dealt with this issue. We are taking our cuts and placing them in phd water. Then soaking our rockwool slabs in a low nute mix ppms around 250 weighing the slabs at about 4-5 pds. then dipping the cuts in clonex gel and finishig it off by placing a dome and putting trays on heat mats. the next day we come in and see a lot of cuts that have turned into bad smelling mush from the bottom to the top. the smell is so bad and the cuts are healthy when we take them. please help!!!!