Oh and to answer your question I have been feeding them miracle grow once a week. That's what I suspected and that is where all the salt damage is coming from. No garden vegetable requires weekly feeding unless it is grown in a container and then only in a well diluted form. And no garden vegetable with the exception of leafy greens like lettuce/chard/spinach requires such high dose nitrogen feeding, much less on a weekly basis. MG and fertilizers like it are ok when used properly. When used excessively the massive amounts of salts they contain build up on the leaves and in the soil. The symptoms on the plants are excessively dark green leaves, burned crispy leaf edges and bleached inter-veinal patches in the leaf tissue. As the leaf tissue is destroyed then bacteria and fungi move in on the destroyed leaf tissues and that is what the yellow patches in the cuke leaf pic might be. Look on the underside of that leaf. If there are black patches of mold or white fuzzy/furry growths then disease is starting. If not then they are just salt damaged patches that haven't faded to white yet. Since these plants are apparently in ground, reduce your MG use to no more often than monthly and preferably no more than every 6 weeks and focus on applying it to the soil and root area, not the leaves. Hope this helps. Dave.

rhizo, thank you for answering. i somehow lost track of this thread, and just found it now. i do use rubbing alcohol mixes from 1/4 to 1/2 on just about everything, including crotons. both indoors and when they are outside. even sometimes give a quick wipe with pure rubbing alcohol if i see scale traces (honeydew): crotons and ivy and citrus are fine with that. and even indoor avocado. cleaned it up quick. i also use it to wipe leaves on amaryllis for greenhouse thrips (am in the middle of that infestation at the moment ;) , in hopes that it will damage the eggs embedded within leaves? (if they are there) - seems ok. sorry to digress, but the only plant that did not like it - was hydrangea (i was controlling powdery mildew with 1/3 solution?) - the leaves dried up and dropped off over sev weeks, not right away, but still... not very good. seems when i ask about stuff in sep threads i don't get many answers. so here it comes....just one more question if you see it: have you ever tried soil drench using alcohol solution? for thrips larvae specifically, but also may be for gnat larvae? i normally use neem oil for that, but it's not totally effective, just slows down things a bit. i search thru the web like a maniac - if it's out there, i'll find it. unfortunately specific info is very difficult to get. i will experiment with hort oil again on just a few ivy branches: diluting it by half to start. they do plague mine on hot balcony and indoors too. and i apologize again for digressing!

Does the new growth have the white spots? I've noticed it only takes a couple hours in the sun to nuke a couple leaves.. But the shape of the burns aren't uniform so.. Is it possible for you to get a picture or 2 of the damage?

Looks like mealy bugs to me too. To find out, get a q-tip; moisten with rubbing alcohol and apply to 'white fuzzy blob'. If mealy, the white fuzz will dissapear, and you should see tiny bug of darker color. Rubbing alcohol will kill it. If there are too many, maybe you should get rid of infected plant, as Morgan suggested. Small infestation could be eradicated by spraying with rubbing alcohol, but you said it looks like it spread to couple of plants - it would be difficult to get rid of them. Problem is that they hide very well, in spots that are difficult to see and treat. Mealy bugs spread easily to other nearby plants. There are some chemicals/systemic sprays that could be used, but I am not sure which ones as I never used any.