Help!

some of my plants are drooping and their lower leaves are yellowing and infront shriveled and dried what can this be?
i think it is either lack of nutes or to much nutes or to much water.
i have done a bit of reading online about the problem but have been unable to make a clearcut decision . I have realised that i need a book so what is the best indoor book for newbies(ed rosenthal) and where can i buy it?

oh yeah another thing could ph be a problem causing nute lock up? i bought this soil and i think the ph is between 6,5 and 7.5 ,thats what the guy said if i remeber corectly but they did grow fine initially so i dont know if that is a problem

Do you have a pic? How often are you watering them and using fert? Is the yellowing starting at the lower leaves and working up or at all the leaves??? You can get many great grow books at your local Barnes and Noble or Borders book stores, just check the gardening section. And you can preview them before buying, unlike buying online.