...have a look into Calcium Deficienies, you seem to have similar foliage marks (tips brown/yellow)...if you agree,use CalMag to correct. You also have signs of Ph related issues, or overwatering (the spots )...if you agree, let the plant dry until the foliage wilts. Water upon wilting and take a mental note of how long it took for the wilting to occur....your objective is to water just before they wilt (this allows air to the roots), this will prevent overwatering....and to correct your ph, once your plants are dry, slowly water them until you get run off water from the bottom of the pot...collect this water and take the ph balance. If your not at where your ph needs to be, you need to flush your plants until you get a good ph. I can't tell your medium, but if in soil/less try to have your ph near 6.5 or maybe a little lower.