We can't be sure about any overfertilization because there isn't a good enough view of the lowest leaves. Your main problems, also mentioned by Snow, are soil Ph and broad-spectrum deficiency. Check the Ph of your soil and all liquids you give the plants immediately. Post what you water them with, feed them and what kind of soil they are in.
While you're picking up a soil Ph tester, you should get some good new fertilizer. A little Guano & Maxicrop would do wonders. If cost is an issue, I was just in a thread posting about cheap ferts:
Blood Meal (N & micros; $1/lb), Bone Meal (P & micros; $.80/lb) and Palm Bunch Ash (0-0-30; $2/lb) should supply all of the nutrients any plants need for any growth period. They are all very cheap but the prices listed are in large bags. I wouldn't grow without Worm Castings as well if I could avoid it.