The studies concluded that many of the injuries previously attributed to fluoride probably were due to unfavorable cultural conditions. Other studies have concluded that fluoride damage is a perlite-related problem and have recommended that you rinse the soil additive in clear water prior to using it in soil mixes. But in light of the available information from testing, you can't blame leaf scorch on perlite, or fluoride, alone. Coffee contains about five times more fluoride than drinking water and tea has even far more than that. Plant foods are sold as salts or as salts dissolved in water.
Salts are stable compounds that, when dissolved in water, can be absorbed by plants.
Fertilizer solutions that aren't taken up by a plant often dry out and so revert to their salty forms. Excess fertilizing can cause brown leaf tips. Unused salts build up in over fertilized soil and damage a plant's roots. This malady can occur even if you fertilize only now and then. If you use too much fertilizer at one time, it won't all be absorbed.