Newly added frag motality rate

[Baldy]

damn this is disheartening. with this last batch of frags i cna understand as ive allowed my maintenance to slip. the summer/winter i havent done as much as i should, but ive still got coralline growing like crazy, and all the frags that i have are growing fine. nitrate, phos are 0, alk 7 (working on bringing it up), calc 440, mag 1300. i can grow chaeto like crazy, and run gfo and carbon. I use RODI water and h2ocean salt. i dose 3 part BRS suppliments through a marine magic doser. the lighting grows the coral i have great, I just cant figure out what the problem is. maybe my skimmer, it doesnt work very well, but would that alone cause the problems?