Need Help Big Time

Hey I cant figure out whats going on with my 8 little red ryder hood plants. Ill tell u about them and post some pictures. Theyre dutch breed auto flower about 3 weeks into bloom Ive only fed once a couple weeks ago at quarter strength so I dont think its nute burn plus Ive been watyering lots of just straight water. It didnt start in all the plants just the smaller ones first but the older leaves (on just a few)started getting spots and kinda going crispy? Now all the plants got it and I cant figure it out. Its in a cabinet with a 150 hps and 3x40w cfls the temps did a couple times a few weeks ago got pretty high but recently daytime temps are between 76-83F and humidity 25-40%. lots of fresh air and circulation whats going on....?