Sounds like too much fertilizer and too much water. Chemical fertilizers will burn roots. Take the plant out of the pot and wash the roots with fresh water. Replant it in fresh potting soil containing no fertilizers or other additives. Pre-moisten the potting soil before potting using 1 part water to 3 parts soil. After potting up the plant water it lightly. If you feel compelled to fertilize use a fish emusion product at half strength once a month. A moisture meter - available online and where house plants are sold, will help you to regulate when to water. Best And Happy Yardening, Nancy.