having a problem the bottom older leavs are turning yellow between the vains and then turning brown n drying out they are seed plants about 30-40 days old ph is 5.8 to 6.0 using pro mix bx with mycorrhize nutes 510 ppm botannicare pro gro my other seed strain cookies kush are beautifull very healthy same with the other strains but these two girls are just starting to look bad ,a few leavs just a littl worried it might spread and end up with a couple sick girls . id apprecate any advice tks