Hey mand I am afraid you may have a few problem with them dear. Salt build up is one problem for sure but it's just caused the other problems that's why different plants are affected. What is the Ph of the soil and what is the Ph of the water you are feeding them with? Toasty brown leafs are a sigh of zinc deficiency and possible a fungus. Intervenal chlorosis and burned tips along with small stunted dark green new growth are caused by excessive salts.